Areas / Email

Email

SMTP, MIME, IMAP and message formats.

565 RFCs · 565 with ISO Plain Language · 0 summaries · 0 index pages

With ISO Plain Language 565

RFC 6376 DKIM DomainKeys Identified Mail (DKIM) Signatures How a domain signs the email it sends, so receivers can check the mail really passed through it unchanged. RFC 2045 MIME Part One Multipurpose Internet Mail Extensions (MIME) Part One: Format of Internet Message Bodies How plain-text email learned to carry pictures, other alphabets and attachments. RFC 2046 MIME media types Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types How an email message says what each piece of it is, and how pieces nest inside one another. RFC 5228 Sieve Sieve: An Email Filtering Language A small, safe language for sorting incoming email by rules, with no loops, variables or shell access. RFC 3461 SMTP DSN Simple Mail Transfer Protocol (SMTP) Service Extension for Delivery Status Notifications (DSNs) How SMTP senders request delivery reports and control the information those reports contain. RFC 2047 MIME Part 3 - Headers Multipurpose Internet Mail Extensions (MIME) Part Three: Message Header Extensions for Non-ASCII Text Encoding non-ASCII text in email headers without breaking existing mail systems RFC 5322 Email Format Internet Message Format Defining the syntax of email messages - headers, body, addresses, and dates - the format behind every email you've ever sent or received. RFC 6409 Mail Submission Message Submission for Mail Why your mail program hands outgoing mail to a submission server on port 587 instead of dropping it into the open mail network. RFC 3463 Enhanced status codes Enhanced Mail System Status Codes A three-part status code that reports mail delivery results in a machine-readable, language-independent form. RFC 3464 DSN message format An Extensible Message Format for Delivery Status Notifications A machine-readable format for reporting email delivery results to senders. RFC 5321 SMTP Simple Mail Transfer Protocol The current standard for Internet email delivery, defining how billions of messages are routed and delivered every day. RFC 7208 SPF Sender Policy Framework (SPF) for Authorizing Use of Domains in Email, Version 1 How domain owners publish which mail servers may use their domain in SMTP identities. RFC 2183 Content-Disposition Communicating Presentation Information in Internet Messages: The Content-Disposition Header Field A MIME header that suggests whether a message part should display inline or as an attachment. RFC 4466 IMAP ABNF extensions Collected Extensions to IMAP4 ABNF One collected grammar for IMAP extensions, with a reusable pattern for adding parameters to existing commands. RFC 8620 JMAP The JSON Meta Application Protocol (JMAP) A JSON protocol for reading and changing server data, synchronizing updates, and transferring files. RFC 2634 S/MIME Enhanced Security Enhanced Security Services for S/MIME Four optional S/MIME services for receipts, message labels, mailing lists, and certificate binding. RFC 3207 SMTP STARTTLS SMTP Service Extension for Secure SMTP over Transport Layer Security An SMTP extension that lets a client and server begin TLS on an existing connection. RFC 2595 IMAP/POP3 over TLS Using TLS with IMAP, POP3 and ACAP How IMAP, POP3 and ACAP begin TLS on an existing connection, and how clients check the server. RFC 5229 Sieve variables Sieve Email Filtering: Variables Extension Adds named variables, string substitution, and tests for Sieve email filters. RFC 3204 MIME media types for ISUP and QSIG Objects MIME types that let SIP messages carry ISUP and QSIG telephone signaling data. RFC 3502 IMAP MULTIAPPEND Internet Message Access Protocol (IMAP) - MULTIAPPEND Extension Upload multiple messages to an IMAP mailbox with one atomic APPEND command. RFC 1870 SMTP SIZE SMTP Service Extension for Message Size Declaration SMTP can check a message's declared size before the client sends its contents. RFC 5965 ARF An Extensible Format for Email Feedback Reports A three-part email report format that people can read and software can process. RFC 4467 IMAP URLAUTH Internet Message Access Protocol (IMAP) - URLAUTH Extension IMAP URLs can grant carefully limited access to a specific message or message part. RFC 6591 ARF Auth Failure Reports Authentication Failure Reporting Using the Abuse Reporting Format An ARF extension reports which email authentication check failed and why. RFC 2920 SMTP pipelining SMTP Service Extension for Command Pipelining How an SMTP client can send command groups without waiting after every command. RFC 8098 MDN Message Disposition Notification A machine-readable email report for what happened to a message after delivery. RFC 2846 GSTN addressing in email GSTN Address Element Extensions in E-mail Services A format for including telephone-network numbers and recipient details in e-mail addresses. RFC 5230 Sieve vacation Sieve Email Filtering: Vacation Extension Adds a controlled vacation auto-reply action to the Sieve email filtering language. RFC 5804 ManageSieve A Protocol for Remotely Managing Sieve Scripts Lets a client securely upload, check, and activate Sieve scripts on a mail server. RFC 2156 MIXER MIXER (Mime Internet X.400 Enhanced Relay): Mapping between X.400 and RFC 822/MIME A gateway specification for mapping messages and addresses between X.400 and Internet mail. RFC 4954 SMTP AUTH SMTP Service Extension for Authentication Adds SASL authentication and sender-identity information to SMTP sessions. RFC 6152 SMTP 8BITMIME SMTP Service Extension for 8-bit MIME Transport How SMTP negotiates support for MIME message bodies containing 8-bit data. RFC 5267 IMAP Contexts Contexts for IMAP4 Adds live update notifications and partial result windows for IMAP search and sort. RFC 6186 SRV for Email Use of SRV Records for Locating Email Submission/Access Services How an email program can discover submission and mailbox servers from the user's email domain. RFC 4731 IMAP SEARCH RETURN IMAP4 Extension to SEARCH Command for Controlling What Kind of Information Is Returned Lets IMAP clients request selected search results instead of every matching message number. RFC 5256 IMAP SORT/THREAD Internet Message Access Protocol - SORT and THREAD Extensions How IMAP servers sort mailbox messages and group them into conversation threads. RFC 6530 Internationalized Email Overview and Framework for Internationalized Email Framework for email addresses and headers that use UTF-8 across mail systems. RFC 8314 TLS for Email Cleartext Considered Obsolete: Use of Transport Layer Security (TLS) for Email Submission and Access Recommends TLS for email submission and access, with a preference for TLS from connection start. RFC 1847 MIME Security Multiparts Security Multiparts for MIME: Multipart/Signed and Multipart/Encrypted A MIME framework for carrying signed or encrypted body parts with their control information. RFC 2231 MIME Parameter Encoding MIME Parameter Value and Encoded Word Extensions MIME parameters can carry other character sets, language information, and long values split into numbered parts. RFC 5092 IMAP URL IMAP URL Scheme A URL format for referring to IMAP servers, mailboxes, messages, and message parts. RFC 5435 Sieve Notify Sieve Email Filtering: Extension for Notifications Add rule-based notifications to Sieve mail filtering, with checks for supported delivery methods. RFC 4314 IMAP ACL IMAP4 Access Control List (ACL) Extension A revised IMAP extension for listing and changing mailbox permissions. RFC 3459 Critical-Content Critical Content Multi-purpose Internet Mail Extensions (MIME) Parameter A Content-Disposition parameter that marks message parts as required or optional for delivery. RFC 4468 SMTP BURL Message Submission BURL Extension A BURL command that lets a mail submission server pull a message from an IMAP server instead of making the client upload it. RFC 4469 IMAP CATENATE Internet Message Access Protocol (IMAP) CATENATE Extension An IMAP extension that builds a new message on the server from new text plus pieces of messages already stored there. RFC 2387 multipart/related The MIME Multipart/Related Content-type A MIME container for a document and the parts it needs to make sense. RFC 3801 VPIM Voice Profile for Internet Mail - version 2 (VPIMv2) A restricted Internet-mail profile for exchanging voice messages between messaging systems. RFC 2449 POP3 Extensions POP3 Extension Mechanism A way for POP3 servers to announce optional commands and behavior before clients use them. RFC 3458 Message-Context header Message Context for Internet Mail A message-level header that hints whether an email is voice mail, fax, paging, or text. RFC 3516 IMAP BINARY IMAP4 Binary Content Extension IMAP can return decoded message data directly, including binary content that contains zero bytes. RFC 2049 MIME Part 5 - Conformance Multipurpose Internet Mail Extensions (MIME) Part Five: Conformance Criteria and Examples Minimum MIME mail-agent requirements, email transport cautions, and an encoding model. RFC 6531 SMTP Internationalization SMTP Extension for Internationalized Email The SMTP extension that lets mail servers agree to carry non-ASCII addresses and UTF-8 headers. RFC 6532 Internationalized Email Internationalized Email Headers Lets email headers and addresses carry Unicode text directly, with no encoded-word tricks. RFC 9051 IMAP4rev2 Internet Message Access Protocol (IMAP) - Version 4rev2 How a mail client reads, searches and manages messages kept in server mailboxes. RFC 2015 MIME Security with PGP MIME Security with Pretty Good Privacy (PGP) How to wrap PGP-encrypted and PGP-signed data inside standard MIME email messages. RFC 3834 Auto-Response to Email Recommendations for Automatic Responses to Electronic Mail Guidance for automatic mail responders to avoid loops, unwanted replies, and unsafe disclosures. RFC 9989 DMARC Domain-Based Message Authentication, Reporting, and Conformance (DMARC) Letting a domain owner say what should happen to email that claims to come from their domain. RFC 2195 CRAM-MD5 IMAP/POP AUTHorize Extension for Simple Challenge/Response Defines CRAM-MD5 challenge-response authentication for IMAP and possible POP3 use. RFC 822 Mail message format STANDARD FOR THE FORMAT OF ARPA INTERNET TEXT MESSAGES The message-content format defined for ARPA Internet text mail, including headers, addresses, dates, and body separation. RFC 4315 IMAP UIDPLUS Internet Message Access Protocol (IMAP) - UIDPLUS extension Small IMAP additions that tell a client the UIDs of messages it just copied or appended, and let it expunge only chosen messages. RFC 9991 DMARC failure reports Domain-Based Message Authentication, Reporting, and Conformance (DMARC) Failure Reporting Per-message DMARC failure reports that tell a domain owner exactly which mail failed authentication. RFC 7162 IMAP CONDSTORE QRESYNC IMAP Extensions: Quick Flag Changes Resynchronization (CONDSTORE) and Quick Mailbox Resynchronization (QRESYNC) How IMAP clients and servers track flag changes and expunged messages so a reconnecting client resyncs fast. RFC 5518 Vouch By Reference Vouch By Reference Lets a third party vouch for the owner of a sending domain, so a mail receiver can check it over DNS. RFC 5617 DKIM ADSP DomainKeys Identified Mail (DKIM) Author Domain Signing Practices (ADSP) A DNS-published statement of how an email domain signs messages, now a Historic mechanism. RFC 3156 MIME OpenPGP MIME Security with OpenPGP How OpenPGP signing and encryption fit inside a MIME email message. RFC 5231 Sieve relational Sieve Email Filtering: Relational Extension Teaching a mail filter to compare values and count the entries in a header. RFC 6533 Internationalized DSNs Internationalized Delivery Status and Disposition Notifications How bounce and read-receipt messages keep an email address that contains characters outside ASCII. RFC 5598 Internet Mail Arch Internet Mail Architecture A shared map of Internet mail's roles, message identities, and transfer components. RFC 1421 PEM Privacy Enhancement for Internet Electronic Mail: Part I: Message Encryption and Authentication Procedures The message-processing and encryption procedures defined for Privacy Enhanced Mail. RFC 3191 GSTN Email Address Minimal GSTN address format in Internet Mail A minimal way to write a telephone number inside an email address, with a registered extension mechanism. RFC 9990 DMARC aggregate reports Domain-Based Message Authentication, Reporting, and Conformance (DMARC) Aggregate Reporting The XML file a mail server sends back to a domain owner showing how its mail was authenticated. RFC 2142 Mailbox Names Mailbox Names for Common Services, Roles and Functions The standard set of email addresses for reaching an organisation's people and services. RFC 2852 DELIVERBY Deliver By SMTP Service Extension Lets a mail sender say by when a message must arrive, and what should happen if it does not. RFC 5464 IMAP METADATA The IMAP METADATA Extension Sticky notes for IMAP: named annotations attached to a mailbox, or to the whole server. RFC 976 UUCP mail format UUCP mail interchange format standard How UUCP hosts carry Internet-style mail addresses without changing the message headers. RFC 2077 MIME Model Type The Model Primary Content Type for Multipurpose Internet Mail Extensions A MIME primary type for three-dimensional models, so CAD and simulation files travel with their meaning intact. RFC 4102 text/red Registration of the text/red MIME Sub-Type The MIME type for sending redundant copies of text, so a lost packet does not lose the words. RFC 3192 Fax Email Address Minimal FAX address format in Internet Mail How to write a fax machine's telephone number as the local part of an ordinary email address. RFC 1731 IMAP4 auth IMAP4 Authentication Mechanisms Three ways an IMAP4 client can prove who it is, and how each one can protect the rest of the session. RFC 2532 Extended Internet Fax Extended Facsimile Using Internet Mail How to fax by email with delivery confirmation, processing confirmation and better quality images. RFC 8621 JMAP for Mail The JSON Meta Application Protocol (JMAP) for Mail How a mail app reads, searches, organises and sends email over JMAP, with one JSON data model instead of IMAP and SMTP plumbing. RFC 3965 Simple Mode IFax A Simple Mode of Facsimile Using Internet Mail How a fax page travels as an ordinary email message, and what a gateway has to do to print it on a real fax machine. RFC 5550 Lemonade profile The Internet Email to Support Diverse Service Environments (Lemonade) Profile A checklist of IMAP, mail submission and Sieve extensions that lets phones and other small clients handle email cheaply. RFC 6068 mailto URI The 'mailto' URI Scheme How a link can open a new email, with the recipient, subject and body already filled in. RFC 8601 Authentication-Results Message Header Field for Indicating Message Authentication Status A standard mail header that records what SPF, DKIM and other checks found about a message. RFC 2369 List-* headers The Use of URLs as Meta-Syntax for Core Mail List Commands and their Transport through Message Header Fields Standard List-* header fields that let mail programs show Subscribe, Unsubscribe and Help buttons for any mailing list. RFC 5258 IMAP LIST Extensions Internet Message Access Protocol version 4 - LIST Command Extensions Extending the IMAP LIST command so a client can ask for subscribed, remote and hierarchical mailboxes in one query. RFC 5465 IMAP NOTIFY The IMAP NOTIFY Extension An IMAP command that lets a client register for the mailstore events it wants the server to push. RFC 5703 Sieve MIME Sieve Email Filtering: MIME Part Tests, Iteration, Extraction, Replacement, and Enclosure Lets a Sieve filtering script look inside a MIME message, walk its parts, and change or wrap what they find. RFC 1422 PEM keys Privacy Enhancement for Internet Electronic Mail: Part II: Certificate-Based Key Management The certificate hierarchy proposed for Privacy Enhanced Mail. RFC 2177 IMAP IDLE IMAP4 IDLE command A command that lets an IMAP client wait while the server pushes mailbox updates in real time. RFC 2683 IMAP4 Impl. Tips IMAP4 Implementation Recommendations Recommendations for IMAP4 client and server authors who want their implementations to interoperate. RFC 3335 MIME business data (EDI) MIME-based Secure Peer-to-Peer Business Data Interchange over the Internet How to send structured business data over email with encryption, a digital signature and a signed receipt. RFC 3886 Tracking Responses An Extensible Message Format for Message Tracking Responses The MIME format a mail server uses to report where a tracked message currently is. RFC 5161 IMAP ENABLE The IMAP ENABLE Extension An IMAP command that lets a client tell the server which extensions it understands. RFC 5182 IMAP SEARCHRES IMAP Extension for Referencing the Last SEARCH Result Lets an IMAP client reuse the result of a SEARCH as the input to the next command, without sending the message list back to the server. RFC 7672 SMTP DANE SMTP Security via Opportunistic DNS-Based Authentication of Named Entities (DANE) Transport Layer Security (TLS) Using DNS-published certificates to make mail server connections resistant to downgrade attacks. RFC 1423 PEM algorithms Privacy Enhancement for Internet Electronic Mail: Part III: Algorithms, Modes, and Identifiers The algorithms, modes, identifiers, and parameters specified for Privacy Enhanced Mail. RFC 3030 SMTP Chunking SMTP Service Extensions for Transmission of Large and Binary MIME Messages Two SMTP extensions: send mail in length-prefixed chunks with BDAT, and send raw binary MIME with no text encoding. RFC 5429 Sieve reject Sieve Email Filtering: Reject and Extended Reject Extensions Lets a Sieve mail filter refuse a message during delivery, so no bounce goes to a forged sender. RFC 7888 IMAP LITERAL+ IMAP4 Non-synchronizing Literals Lets IMAP clients send string data without waiting for the server's go-ahead, saving a network round trip. RFC 2342 IMAP NAMESPACE IMAP4 Namespace A command that lets a mail client ask a server which prefixes it uses for personal, shared and other users' mailboxes. RFC 2505 Anti-Spam SMTP Anti-Spam Recommendations for SMTP MTAs A Best Current Practice list of the checks a mail server should make to reduce the damage from spam. RFC 4289 MIME registration Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures How new MIME access types and transfer encodings get registered, and what a proposal must satisfy. RFC 2034 SMTP Enhanced Errors SMTP Service Extension for Returning Enhanced Error Codes Lets an SMTP server say exactly why a delivery worked or failed, using codes that software can read. RFC 2311 S/MIME v2 S/MIME Version 2 Message Specification How S/MIME version 2 applies signatures and encryption to MIME entities using PKCS #7. RFC 2912 Indicating Media Features for MIME Content A MIME header that labels a message part with the media features needed to handle it. RFC 3885 SMTP Message Tracking SMTP Service Extension for Message Tracking A way for a sender to tag an outgoing email so its fate can be looked up later if no delivery notice ever arrives. RFC 4865 FUTURERELEASE SMTP Submission Service Extension for Future Message Release How a mail client can ask its submission server to hold a message and release it at a later time. RFC 5255 IMAP i18n Internet Message Access Protocol Internationalization IMAP extensions for language negotiation, translated folder prefixes and international search, sort and threading. RFC 5819 IMAP LIST-STATUS IMAP4 Extension for Returning STATUS Information in Extended LIST Lets an IMAP client list mailboxes and fetch their message counts in one command instead of one STATUS call per mailbox. RFC 6590 Abuse Report Redaction Redaction of Potentially Sensitive Data from Mail Abuse Reports How to hide who complained in an email abuse report while still letting the receiver spot repeat complaints about the same person. RFC 6785 Sieve IMAP events Support for Internet Message Access Protocol (IMAP) Events in Sieve Lets Sieve mail filters run when IMAP messages are added or flagged, not only when mail is delivered. RFC 6851 IMAP MOVE Internet Message Access Protocol (IMAP) - MOVE Extension One IMAP command that moves messages between mailboxes instead of copying and then deleting. RFC 6857 Post-Delivery Message Downgrading for Internationalized Email Messages How a POP or IMAP server rewrites internationalized email into plain ASCII headers so old clients can still read it. RFC 8474 IMAP OBJECTID IMAP Extension for Object Identifiers Gives IMAP mailboxes and messages permanent IDs, so a client can tell that something merely moved instead of downloading it again. RFC 9394 IMAP PARTIAL IMAP PARTIAL Extension for Paged SEARCH and FETCH How IMAP clients can ask for a slice of a big search or fetch result instead of everything at once. RFC 1176 IMAP2 Interactive Mail Access Protocol: Version 2 A protocol for reading and managing mail stored on a mailbox server. RFC 3676 text/plain format The Text/Plain Format and DelSp Parameters How a trailing space lets plain-text email reflow to any screen while still reading as ordinary text. RFC 3802 audio/32KADPCM Toll Quality Voice - 32 kbit/s Adaptive Differential Pulse Code Modulation (ADPCM) MIME Sub-type Registration Registers the MIME type that carries 32 kbit/s ADPCM telephone-quality voice, with a fixed bit order. RFC 3803 Content Duration MIME Header Definition A one-line mail header that states how many seconds an audio or video attachment lasts. RFC 5235 Sieve spamtest Sieve Email Filtering: Spamtest and Virustest Extensions Portable Sieve tests that read a spam or virus score instead of a scanner's own header format. RFC 6856 Post Office Protocol Version 3 (POP3) Support for UTF-8 How POP3 learns to carry UTF-8 text in mail, login names, passwords and server messages. RFC 7377 IMAP Multisearch IMAP4 Multimailbox SEARCH Extension One IMAP command that searches many mailboxes at once, without disturbing the one you have open. RFC 821 SMTP (Original) Simple Mail Transfer Protocol The original specification for email delivery, still in use (updated) over 40 years later RFC 561 Mail Headers Standardizing Network Mail Headers An interim proposal to give network mail one standard From, Date and Subject header. RFC 2785 Methods for Avoiding the "Small-Subgroup" Attacks on the Diffie-Hellman Key Agreement Method for S/MIME When Diffie-Hellman public keys need checks to resist small-subgroup attacks. RFC 937 POP2 Post Office Protocol: Version 2 An early protocol for a workstation to retrieve mail from a mailbox server. RFC 1801 MHS Routing in X.500 MHS use of the X.500 Directory to support MHS Routing An experimental design for using X.500 directory data to route X.400 mail. RFC 2157 X.400/MIME Bodies Mapping between X.400 and RFC-822/MIME Message Bodies Rules for turning the parts of an X.400 message into MIME parts, and back, at a mail gateway. RFC 2919 List-Id List-Id: A Structured Field and Namespace for the Identification of Mailing Lists A mail header that gives each mailing list a stable, domain-based identifier. RFC 4959 IMAP SASL-IR IMAP Extension for Simple Authentication and Security Layer (SASL) Initial Client Response Lets an IMAP client send its first SASL authentication data with the AUTHENTICATE command, saving a round trip. RFC 5068 Email Submission Operations Email Submission Operations: Access and Accountability Requirements Operational rules that make the first hop of email, from a user's mail program to a mail server, accountable. RFC 5232 Sieve imap4flags Sieve Email Filtering: Imap4flags Extension Lets Sieve mail filters set, add, remove and test IMAP flags on a message as it is delivered. RFC 5293 Sieve Editheader Sieve Email Filtering: Editheader Extension Two Sieve actions that let a mail filter script add header fields to a message and delete them. RFC 5490 Sieve mailbox extensions The Sieve Mail-Filtering Language -- Extensions for Checking Mailbox Status and Accessing Mailbox Metadata New Sieve tests that check whether a mailbox exists, read mailbox and server annotations, and create missing folders. RFC 6134 Sieve External Lists Sieve Extension: Externally Stored Lists Reference externally managed lists in email filter rules without rewriting the script. RFC 6650 ARF Applicability Creation and Use of Email Feedback Reports: An Applicability Statement for the Abuse Reporting Format (ARF) Practical advice on when, where and how to send machine-readable email abuse and authentication-failure reports. RFC 6652 SPF Failure Reports Sender Policy Framework (SPF) Authentication Failure Reporting Using the Abuse Reporting Format Three new SPF record settings let a domain ask receivers to mail back reports when SPF checks fail. RFC 6858 Simplified POP and IMAP Downgrading for Internationalized Email A deliberately simple way for IMAP and POP servers to show internationalized mail to old clients, with some information lost. RFC 8580 Sieve FCC Sieve Extension: File Carbon Copy (FCC) How a Sieve mail filter can keep a copy of the automatic replies and notifications it sends for you. RFC 2789 Mail Monitoring MIB Mail Monitoring MIB SNMP objects that let a management system watch message flow, queues and errors inside a mail server. RFC 1896 text/enriched The text/enriched MIME Content-type A small set of formatting commands for enriched text in MIME email. RFC 2822 Internet Message Format Internet Message Format The syntax for email headers and text bodies exchanged between computer users. RFC 1864 Content-MD5 The Content-MD5 Header Field An optional MIME field that carries a digest for checking whether content changed in transit. RFC 2557 MHTML MIME Encapsulation of Aggregate Documents, such as HTML (MHTML) How to pack an HTML page and everything it references into one MIME message, and how links find their parts. RFC 5034 POP3 SASL The Post Office Protocol (POP3) Simple Authentication and Security Layer (SASL) Authentication Mechanism How a POP3 client logs in using any SASL mechanism, with the AUTH command and the SASL capability. RFC 2033 LMTP Local Mail Transfer Protocol A mail-transfer protocol that returns a separate delivery result for each recipient. RFC 680 Message Transmission Protocol A proposed set of message fields extending the format in RFC 561. RFC 934 Proposed standard for message encapsulation A proposed format for wrapping mail messages so a recipient can extract them again. RFC 1424 PEM certification Privacy Enhancement for Internet Electronic Mail: Part IV: Key Certification and Related Services Email procedures for PEM key certification and certificate revocation lists. RFC 1056 PCMAIL PCMAIL: A distributed mail system for personal computers A distributed mail system with local copies and a simple synchronization protocol. RFC 1846 SMTP 521 SMTP 521 Reply Code An SMTP reply code for a host that does not accept incoming mail. RFC 1521 MIME MIME (Multipurpose Internet Mail Extensions) Part One: Mechanisms for Specifying and Describing the Format of Internet Message Bodies How MIME labels email content and encodes data for mail transport. RFC 1049 Content-Type header Content-type header field for Internet messages A proposed mail header that tells a reading program what kind of content a message body really holds. RFC 1767 MIME EDI MIME Encapsulation of EDI Objects How to carry electronic data interchange documents as MIME body parts, using three content types. RFC 1848 MOSS MIME Object Security Services Signing and encrypting MIME email with plain public key pairs, no certificates required. RFC 2480 Gateways and MIME Security Multiparts What mail gateways to non-MIME systems must do so signed and encrypted messages are not silently broken. RFC 3362 image/t38 MIME type Real-time Facsimile (T.38) - image/t38 MIME Sub-type Registration Registers image/t38 for identifying real-time T.38 facsimile media in SDP. RFC 3503 MDN for IMAP Message Disposition Notification (MDN) profile for Internet Message Access Protocol (IMAP) How several mail programs sharing one IMAP mailbox avoid sending the same read receipt twice. RFC 3865 SMTP No Soliciting A No Soliciting Simple Mail Transfer Protocol (SMTP) Service Extension An SMTP extension that works like a No Soliciting sign: a mail server says which kinds of solicitation it does not want. RFC 4262 S/MIME capabilities cert X.509 Certificate Extension for Secure/Multipurpose Internet Mail Extensions (S/MIME) Capabilities An X.509 certificate extension for stating an entity's S/MIME capabilities. RFC 4406 Sender ID Sender ID: Authenticating E-Mail A DNS-based test of whether a mail server is authorized to send for an email domain. RFC 5064 Archived-At header The Archived-At Message Header Field An email header that points straight to the archived copy of that one message. RFC 5173 Sieve body Sieve Email Filtering: Body Extension How a Sieve mail filter can look inside the body of a message, not just its headers. RFC 5259 IMAP CONVERT Internet Message Access Protocol - CONVERT Extension An IMAP extension that lets a client ask the server to convert attachments and headers before download. RFC 5423 Message Store Events Internet Message Store Events A common list of the things a mail store can report, such as new mail, deleted messages and quota changes. RFC 5436 Sieve mailto Sieve Notification Mechanism: mailto How a Sieve mail filter can ping you by sending a brand-new email, without starting a mail loop. RFC 6154 IMAP Special-Use IMAP LIST Extension for Special-Use Mailboxes How an IMAP server can tell your mail client which folder is Drafts, Sent, Trash and so on. RFC 6651 DKIM Failure Reports Extensions to DomainKeys Identified Mail (DKIM) for Failure Reporting How a domain can ask receivers to report back when its DKIM signatures fail to verify. RFC 6657 MIME charset Update Update to MIME regarding "charset" Parameter Handling in Textual Media Types Retires the old rule that text media types without a charset parameter are assumed to be US-ASCII. RFC 6692 ARF Source Port Source Ports in Abuse Reporting Format (ARF) Reports An ARF field for recording the TCP source port associated with an abuse report. RFC 6710 SMTP MT-PRIORITY Simple Mail Transfer Protocol Extension for Message Transfer Priorities A way for a mail message to carry a priority from -9 to 9 so busy servers can move urgent mail first. RFC 7372 Email Authentication Status Codes New SMTP status codes that tell a sender its message was refused because it failed email authentication checks. RFC 7504 SMTP 521 and 556 Reply Codes Two SMTP reply codes that let a host say plainly: this machine does not accept mail at all. RFC 8301 DKIM Crypto Update Cryptographic Algorithm and Key Usage Update to DomainKeys Identified Mail (DKIM) DKIM requires rsa-sha256 and retires rsa-sha1 for signing and verification. RFC 8461 MTA-STS SMTP MTA Strict Transport Security (MTA-STS) How a mail domain can tell senders: deliver to us only over properly authenticated TLS. RFC 8579 Sieve Special-Use Sieve Email Filtering: Delivering to Special-Use Mailboxes Lets a Sieve mail filter file messages into the Junk, Sent or Archive folder by its job rather than its name. RFC 8616 Email Auth for IDN Email Authentication for Internationalized Mail Settles which form of an internationalized domain name SPF, DKIM and DMARC must use, so mail with non-ASCII addresses can be authenticated. RFC 9007 JMAP MDN Handling Message Disposition Notification with the JSON Meta Application Protocol (JMAP) How a JMAP mail client sends and reads read receipts through two small methods, MDN/send and MDN/parse. RFC 9404 JMAP Blob JSON Meta Application Protocol (JMAP) Blob Management Extension JMAP extension for creating and reading blobs inside ordinary method calls, plus a reverse lookup of where blobs are used. RFC 9670 JMAP Sharing JSON Meta Application Protocol (JMAP) Sharing A common JMAP model for principals, share notifications and per-object sharing rights. RFC 1465 Routing Coordination for X.400 MHS Services Within a Multi Protocol / Multi Network Environment Table Format V3 for Static Routing A V3 table format for coordinating X.400 mail routing across domains, relays and networks. RFC 1641 Unicode in MIME Using Unicode with MIME How to identify and encode Unicode 1.1 text in MIME messages. RFC 2048 Multipurpose Internet Mail Extensions (MIME) Part Four: Registration Procedures The registration rules RFC 2048 defined for MIME media types and related values. RFC 1524 Mailcap A User Agent Configuration Mechanism For Multimedia Mail Format Information A shared file format for telling mail programs which local tools handle each media type. RFC 1733 IMAP4 mail models Distributed Electronic Mail Models in IMAP4 Three client-server email models and how IMAP4 can support each one. RFC 4021 Registration of Mail and MIME Header Fields The first official IANA list of permanent mail and MIME header fields, from Date and Subject to Content-Type. RFC 4143 IFax ENUM service Facsimile Using Internet Mail (IFAX) Service of ENUM The E2U+ifax ENUM service lets a telephone number resolve to an email address for Internet fax. RFC 6377 DomainKeys Identified Mail (DKIM) and Mailing Lists Best practices for keeping DKIM useful when mailing lists rewrite the messages that pass through them. RFC 6449 Complaint feedback loops Complaint Feedback Loop Operational Recommendations How mailbox providers tell senders that a user marked their mail as spam, and what both sides should do with that. RFC 1869 SMTP Extensions SMTP Service Extensions How a mail server announces its optional features, starting with the EHLO greeting. RFC 2821 SMTP Simple Mail Transfer Protocol The rulebook for moving email between servers: the commands, the replies, and who does what when a message cannot be delivered. RFC 2061 IMAP4 and IMAP2bis IMAP4 Compatibility with IMAP2bis Compatibility notes for IMAP4 implementations that need to communicate with IMAP2bis servers or clients. RFC 524 Mail Protocol Proposed Mail Protocol A proposed mail subsystem for FTP with delivery, forwarding, recording, and verification functions. RFC 759 MPM Internet Message Protocol A structured system for moving messages between processing modules on connected networks. RFC 767 Structured format for transmission of multi-media documents A structured format for messages that combine text, graphics, facsimile, and voice. RFC 1328 X.400 Downgrading X.400 1988 to 1984 downgrading Guidance for converting X.400 (1988) messages and addresses for X.400 (1984) systems. RFC 1327 X.400 to RFC 822 Mapping between X.400(1988) / ISO 10021 and RFC 822 How a gateway turns an X.400 message into an Internet mail message, and back again. RFC 3798 MDN Message Disposition Notification How a mail system tells the sender what happened to a message after it was delivered. RFC 3302 image/tiff MIME type Tag Image File Format (TIFF) - image/tiff MIME Sub-type Registration The official registration of image/tiff, the MIME label for TIFF pictures. RFC 3950 TIFF-FX MIME Type Tag Image File Format Fax eXtended (TIFF-FX) - image/tiff-fx MIME Sub-type Registration Registers image/tiff-fx, the MIME type for Internet fax image files. RFC 5233 Sieve subaddress Sieve Email Filtering: Subaddress Extension Lets Sieve mail filters look at the user and detail parts of addresses like ken+sieve@example.org. RFC 6318 Suite B in Secure/Multipurpose Internet Mail Extensions (S/MIME) Which NSA Suite B algorithms an S/MIME email system uses, and how to plug them into signing and encryption. RFC 9208 IMAP QUOTA IMAP QUOTA Extension How an IMAP client asks a mail server how much space it has used, and what the limit is. RFC 9755 IMAP UTF-8 IMAP Support for UTF-8 How IMAP servers and clients negotiate UTF-8 for mailbox names, quoted strings and internationalized message headers. RFC 1437 The Extension of MIME Content-Types to a New Medium An April 1st joke that proposes a MIME type for transporting sentient life forms. RFC 1732 IMAP4 compatibility IMAP4 Compatibility with IMAP2 and IMAP2bis Hints for IMAP4 clients and servers that need to communicate with older IMAP2 software. RFC 2062 IMAP Obsolete Syntax Internet Message Access Protocol - Obsolete Syntax The old IMAP4 commands and responses that a server may still meet, and need not support. RFC 2076 Common Message Headers Common Internet Message Headers One table of the header fields that turn up at the top of email and news messages, and what each one means. RFC 2180 IMAP4 Multi-Accessed Mailbox Practice What an IMAP4 server may do when several clients are using the same mailbox at once. RFC 3114 Implementing Company Classification Policy with the S/MIME Security Label How to mark signed email with a company's own classification levels, so a recipient's system can act on them. RFC 4134 S/MIME Examples Examples of S/MIME Messages Worked examples of signed, encrypted and hashed mail, so that implementations can check their output against the same bytes. RFC 4549 Disconnected IMAP4 sync Synchronization Operations for Disconnected IMAP4 Clients How a mail client that works offline should use IMAP commands to bring its local copy back in step with the server. RFC 4686 DKIM threat analysis Analysis of Threats Motivating DomainKeys Identified Mail (DKIM) The threats that signature-based email authentication was designed to address RFC 5585 DKIM overview DomainKeys Identified Mail (DKIM) Service Overview How DKIM lets an organisation sign a message and be checked on it. RFC 7960 DMARC & Indirect Mail Interoperability Issues between Domain-based Message Authentication, Reporting, and Conformance (DMARC) and Indirect Email Flows Why strict DMARC policies break mailing lists, forwarders and other mail that does not travel straight from author to reader. RFC 3555 MIME Type Registration of RTP Payload Formats Giving every RTP payload format a MIME type name, so text-based protocols can say what a stream carries. RFC 1740 MacMIME MIME Encapsulation of Macintosh Files - MacMIME How to mail a two-part Macintosh file through MIME without losing either part. RFC 1985 SMTP ETRN SMTP Service Extension for Remote Message Queue Starting ETRN lets a mail client ask a server to start sending the mail it is holding for that client. RFC 2017 URL External-Body Type Definition of the URL MIME External-Body Access-Type A MIME access type that points to external content using a URL. RFC 2158 X.400 Image Body Parts X.400 body-part identifiers and MIME mappings for JPEG and GIF images. RFC 2160 Carrying PostScript in X.400 and MIME Two X.400 carriers for PostScript and their mapping to MIME application/postscript. RFC 2193 IMAP4 Referrals IMAP4 Mailbox Referrals How an IMAP server can point a client to another server that holds a mailbox. RFC 2913 MIME type feature tag MIME Content Types in Media Feature Expressions A media feature tag called type that lets a capability expression say which MIME content types it covers. RFC 2971 IMAP ID IMAP4 ID extension An IMAP command that lets clients and servers tell each other what software they are, for bug reports and statistics. RFC 3003 audio/mpeg The audio/mpeg Media Type The registered MIME media type for MPEG-1 and MPEG-2 audio streams. RFC 3206 POP SYS and AUTH The SYS and AUTH POP Response Codes Two POP3 error codes and a capability that tell a mail client whether a failed login is the user's fault or the server's. RFC 3691 IMAP UNSELECT Internet Message Access Protocol (IMAP) UNSELECT command An IMAP command that closes the selected mailbox without expunging deleted messages. RFC 3804 VPIM Addressing Voice Profile for Internet Mail (VPIM) Addressing How to write email addresses that point at voice mailboxes, outdialing devices and AMIS voice networks. RFC 3848 ESMTP and LMTP Types ESMTP and LMTP Transmission Types Registration Seven keywords for recording ESMTP and LMTP transport details in Received headers. RFC 3854 S/MIME for X.400 Securing X.400 Content with Secure/Multipurpose Internet Mail Extensions (S/MIME) How to sign and encrypt the contents of an X.400 message using the same S/MIME and CMS machinery as Internet mail. RFC 3855 S/MIME in X.400 Transporting Secure/Multipurpose Internet Mail Extensions (S/MIME) Objects in X.400 How to carry S/MIME-protected objects inside native X.400 messages, and how to label them. RFC 3894 Sieve Copy Sieve Extension: Copying Without Side Effects A Sieve :copy parameter for filing or redirecting a copy without changing normal delivery. RFC 3938 Video-Message Message-Context A Message-Context value for email whose primary content is video. RFC 3939 Calling Line Identification for Voice Mail Messages Two mail headers that keep a caller's number and name with a stored voice mail message. RFC 4141 SMTP and MIME Extensions for Content Conversion How mail servers along the way can convert a message into a form the recipient can handle, with the sender's permission. RFC 4142 FFPIM Full-mode Fax Profile for Internet Mail (FFPIM) Closing the gap between email-based fax and classic fax with content negotiation and richer TIFF. RFC 4407 Purported Resp. Address Purported Responsible Address in E-Mail Messages A rule for finding, from the headers alone, who a message says last put it into the mail system. RFC 4978 IMAP COMPRESS The IMAP COMPRESS Extension How an IMAP client and server agree to squeeze everything they send each other with DEFLATE. RFC 5183 Sieve environment Sieve Email Filtering: Environment Extension A Sieve extension that lets an email filter script ask about the system it is running on. RFC 5437 Sieve XMPP Sieve Notification Mechanism: Extensible Messaging and Presence Protocol (XMPP) How a Sieve mail filter can ping you with an XMPP (Jabber) instant message when new mail arrives. RFC 5530 IMAP response codes IMAP Response Codes Seventeen named reasons an IMAP server can give, in a form programs can read, when it says no. RFC 5593 IMAP URL access IDs Internet Message Access Protocol (IMAP) - URL Access Identifier Extension New access identifiers for URLAUTH IMAP URLs, so services such as streaming can fetch mail on a user's behalf without abusing submit+. RFC 5957 IMAP SORT display Display-Based Address Sorting for the IMAP4 SORT Extension IMAP sort criteria that use displayed names in From and To addresses. RFC 6131 Sieve Vacation Seconds Sieve Vacation Extension: "Seconds" Parameter A Sieve vacation parameter for setting the auto-reply interval in seconds. RFC 6132 Sieve Presence Sieve Notification Using Presence Information Lets a Sieve mail filter check whether you are busy, away or offline before it decides how to notify you. RFC 6203 IMAP fuzzy search IMAP4 Extension for Fuzzy Search An IMAP extension that lets servers match mail loosely and score each hit by relevancy. RFC 6609 Sieve Include Sieve Email Filtering: Include Extension Lets one Sieve email filter script pull in another, with shared variables and personal or site-wide libraries. RFC 6854 Group From: Update to Internet Message Format to Allow Group Syntax in the "From:" and "Sender:" Header Fields Email's From: and Sender: headers may now use group syntax, mainly so a message can say it has no address to reply to. RFC 7505 Null MX A "Null MX" No Service Resource Record for Domains That Accept No Mail A single MX record that tells the world a domain accepts no email, so senders give up at once. RFC 7889 IMAP APPENDLIMIT The IMAP APPENDLIMIT Extension An IMAP extension that tells clients the largest message a server will accept before they upload it. RFC 8058 Signaling One-Click Functionality for List Email Headers A signed email header that tells mail systems they can unsubscribe a user with one automatic HTTPS POST. RFC 8457 IMAP \Important IMAP "$Important" Keyword and "\Important" Special-Use Attribute A message keyword and a folder attribute that let IMAP servers say 'this mail is probably important to you'. RFC 8460 SMTP TLS Reporting SMTP TLS Reporting How mail senders tell recipient domains when encrypted delivery worked, failed, or was attacked. RFC 8463 DKIM Ed25519 A New Cryptographic Signature Method for DomainKeys Identified Mail (DKIM) Adds Ed25519-SHA256 to DKIM: a signature scheme with much shorter keys than RSA, which every verifier must support. RFC 9042 Sieve MAILBOXID Sieve Email Filtering: Delivery by MAILBOXID Lets Sieve mail filters file messages by a mailbox's permanent ID, so renaming a folder does not break the rules. RFC 9425 JMAP Quotas JSON Meta Application Protocol (JMAP) for Quotas A JMAP data type that lets a client see how much of its allowance it has used, and where the limits are. RFC 10022 IMAP UIDBATCHES IMAP UIDBATCHES Extension An IMAP command that hands a client ready-made UID ranges for working through a big mailbox in equal batches. RFC 4871 DKIM DomainKeys Identified Mail (DKIM) Signatures Signing an email message so a receiver can confirm the sending domain really sent it. RFC 5751 S/MIME 3.2 Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.2 Message Specification How a mail message is signed, encrypted and compressed using MIME and the Cryptographic Message Syntax. RFC 7489 DMARC Domain-based Message Authentication, Reporting, and Conformance (DMARC) How a domain owner says what to do with mail that claims to come from it but fails its authentication checks. RFC 987 X.400 to RFC 822 Mapping between X.400 and RFC 822 The rules a mail gateway follows to translate messages between X.400 systems and RFC 822 Internet mail. RFC 5257 IMAP ANNOTATE Internet Message Access Protocol - ANNOTATE Extension How an IMAP server can store comments, flags and other notes on messages and on individual message parts. RFC 5451 Auth-Results Header Message Header Field for Indicating Message Authentication Status One mail header that says what each authentication check found. RFC 7001 Message Header Field for Indicating Message Authentication Status A mail header that records which authentication checks passed, and which did not. RFC 3851 S/MIME 3.1 Messages Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Message Specification The message formats, algorithms and rules used to sign and encrypt mail with S/MIME version 3.1. RFC 2060 IMAP4rev1 Internet Message Access Protocol - Version 4rev1 The protocol a mail client uses to read and change the mailboxes stored on a mail server. RFC 1844 MIME UA Checklist Multimedia E-mail (MIME) User Agent Checklist A questionnaire for judging how well an email program handles MIME, plus a responder that mails you test messages. RFC 2152 UTF-7 UTF-7 A Mail-Safe Transformation Format of Unicode A way to write any Unicode text using only 7-bit ASCII, so it survives old mail systems. RFC 3656 MUPDATE The Mailbox Update (MUPDATE) Distributed Mailbox Database Protocol A small text protocol that lets many mail servers share one authoritative list of which mailbox lives where. RFC 6783 Lists & non-ASCII Mailing Lists and Non-ASCII Addresses What a mailing list has to decide when some of its members have email addresses that are not plain ASCII. RFC 974 MX routing Mail routing and the domain system How a mail server was told to pick the right host to deliver a message to. RFC 1894 DSN Message Format An Extensible Message Format for Delivery Status Notifications A standard, machine-readable format for a mail server to report what happened to a message it tried to deliver. RFC 2633 S/MIME v3 S/MIME Version 3 Message Specification How signatures and encryption are added to MIME messages, and which formats carry them. RFC 1522 MIME headers MIME (Multipurpose Internet Mail Extensions) Part Two: Message Header Extensions for Non-ASCII Text How non-ASCII text is written into email headers so that old and new mail programs both cope. RFC 1341 MIME MIME (Multipurpose Internet Mail Extensions): Mechanisms for Specifying and Describing the Format of Internet Message Bodies How an email body can carry several kinds of content, in any character set, without losing anything. RFC 4408 SPF v1 Sender Policy Framework (SPF) for Authorizing Use of Domains in E-Mail, Version 1 How a domain publishes, in DNS, which mail servers may send email using its name, and how receivers check it. RFC 475 FTP FTP and Network Mail System A discussion of how FTP could support sending, storing, and distributing network mail. RFC 555 Responses to critiques of the proposed mail protocol James White's answers to comments on the proposed mail protocol in RFC 524. RFC 630 FTP FTP error code usage for more reliable mail service How TENEX mail systems used FTP reply codes to decide whether to retry delivery. RFC 753 Internet Message Protocol Internet Message Protocol A message format and routing protocol for mail moving between networks. RFC 785 Mail Transfer Protocol: ISI TOPS20 file definitions The file formats connecting TOPS-20 mail creation programs to MTP. RFC 1047 Duplicate messages and SMTP Why SMTP can deliver a message twice when the final acknowledgment is lost. RFC 1090 SMTP on X.25 SMTP on X.25 Procedures for carrying SMTP sessions directly over X.25 virtual circuits. RFC 1496 Rules for downgrading messages from X.400/88 to X.400/84 when MIME content-types are present in the messages Rules for carrying MIME content through an older X.400 mail system. RFC 4405 SMTP SUBMITTER SMTP Service Extension for Indicating the Responsible Submitter of an E-Mail Message An SMTP extension that names the party most recently responsible for putting a message into the mail system. RFC 6522 Multipart/Report The Multipart/Report Media Type for the Reporting of Mail System Administrative Messages The MIME container that wraps a mail system report: a human note, a machine-readable account and, optionally, the original message. RFC 1428 Transition of Internet Mail from Just-Send-8 to 8bit-SMTP/MIME Moving email from informal 8-bit extensions to the standard MIME protocol RFC 1506 A Tutorial on Gatewaying between X.400 and Internet Mail How to translate mail between X.400 and Internet standards using RFC 1327 mapping rules RFC 1556 Handling of Bi-directional Texts in MIME MIME character-set suffixes for visual, implicit, and explicit text direction. RFC 1615 Migrating from X.400(84) to X.400(88) Planning the upgrade from X.400(84) to the newer X.400(88) email standard. RFC 1649 Operational Requirements for X.400 Management Domains in the GO-MHS Community Rules for connecting global X.400 email services into one community. RFC 1685 Writing X.400 O/R Names A uniform way for people to write down the many-part addresses used by X.400 email. RFC 2162 MaXIM-11 MaXIM-11 - Mapping between X.400 / Internet mail and Mail-11 mail Rules for translating addresses and message elements between DECnet Mail-11, X.400 and Internet mail. RFC 3098 How to Advertise Responsibly Using E-Mail and Newsgroups or - how NOT to $$$$$ MAKE ENEMIES FAST! $$$$$ Guidelines for ethical email and newsgroup marketing RFC 3348 IMAP4 CHILDREN The Internet Message Action Protocol (IMAP4) Child Mailbox Extension Two IMAP LIST attributes that tell a mail client whether a mailbox has child mailboxes RFC 3773 High-Level Requirements for Internet Voice Mail What voice mail systems must do to work together over the Internet. RFC 4024 VPIM Client Behaviour Voice Messaging Client Behaviour How an email client should show and handle voice and fax mail, from the icon to the read flag. RFC 4146 Simple New Mail Notification A simple technique for notifying a client when new mail arrives. RFC 4155 application/mbox The application/mbox Media Type The MIME type and standard format for mailbox files containing email messages. RFC 4496 OPES SMTP use cases Open Pluggable Edge Services (OPES) SMTP Use Cases Practical applications for processing email at network gateways using the OPES framework. RFC 4952 Internationalized Email Overview and Framework for Internationalized Email The roadmap for letting email addresses and headers use people's own names and scripts, in UTF-8. RFC 5016 DKIM SSP Requirements Requirements for a DomainKeys Identified Mail (DKIM) Signing Practices Protocol Requirements for publishing DKIM signing practices to help detect spoofed mail. RFC 5383 Lemonade Deployment Deployment Considerations for Lemonade-Compliant Mobile Email What networks, firewalls and NATs must allow so that mobile email over IMAP and Message Submission works. RFC 5442 LEMONADE Architecture LEMONADE Architecture - Supporting Open Mobile Alliance (OMA) Mobile Email (MEM) Using Internet Mail How ordinary Internet mail protocols map onto the Open Mobile Alliance's architecture for email on mobile devices. RFC 5863 DKIM Operations DomainKeys Identified Mail (DKIM) Development, Deployment, and Operations Practical advice for building, deploying and running DKIM email signing, from key handling to mailing lists. RFC 8755 CNSA suite in S/MIME Using Commercial National Security Algorithm Suite Algorithms in Secure/Multipurpose Internet Mail Extensions Using NSA-approved cryptographic algorithms in secure email. RFC 4409 Mail Submission Port 587 Message Submission for Mail Why mail clients should hand outgoing mail to a separate submission server, normally on port 587. RFC 2440 OpenPGP OpenPGP Message Format The packet formats that let different programs encrypt, sign and exchange OpenPGP data. RFC 733 Standard for the format of ARPA network text messages Defines a structured header and body format for text messages on the ARPA Network. RFC 1026 X.400 to RFC 822 Addendum to RFC 987: (Mapping between X.400 and RFC-822) Adds ordering rules and omitted-component support to the X.400 and RFC 822 mapping. RFC 1651 SMTP Extensions SMTP Service Extensions The EHLO handshake that lets an SMTP server announce which optional features it supports. RFC 2421 VPIM v2 Voice Profile for Internet Mail - version 2 Standard format for sending voice mail messages over Internet email. RFC 4551 IMAP CONDSTORE IMAP Extension for Conditional STORE Operation or Quick Flag Changes Resynchronization Conditional flag updates and quick resynchronization for shared IMAP mailboxes. RFC 3850 S/MIME 3.1 Certificates Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.1 Certificate Handling How S/MIME email agents validate and use X.509 certificates. RFC 1425 ESMTP SMTP Service Extensions A framework for adding new features to SMTP without breaking old implementations RFC 1893 Enhanced Status Codes Enhanced Mail System Status Codes Machine-readable codes that say exactly what went wrong with email delivery. RFC 2192 IMAP URL IMAP URL Scheme A standard way to write a link to an IMAP server, a mailbox, a search result, a message or one part of a message. RFC 2368 mailto URL The mailto URL scheme Web links that open your email program with a message ready to send. RFC 2426 vCard 3.0 vCard MIME Directory Profile A standard format for exchanging digital business cards and contact information RFC 3028 Sieve Sieve: A Mail Filtering Language A safe, scriptable language for filtering email at delivery time. RFC 278 Revision of the Mail Box Protocol Revises the ARPANET Mail Box Protocol for ASCII text and printer delivery. RFC 402 ARPA Network Mailing Lists Three mailing lists used by the Network Information Center to distribute documents. RFC 841 Specification for message format for Computer Based Message Systems A US federal standard for what goes inside an electronic message, republished as an RFC for ARPA researchers. RFC 1203 IMAP3 Interactive Mail Access Protocol: Version 3 The third version of IMAP, which made the server rather than the workstation the holder of the mailbox. RFC 2161 A MIME Body Part for ODA The application/oda MIME type carries Office Document Architecture data. RFC 2298 MDN An Extensible Message Format for Message Disposition Notifications A standard format for email read receipts and delivery confirmations. RFC 9586 IMAP UIDONLY IMAP Extension for Using and Returning Unique Identifiers (UIDs) Only An IMAP extension that drops message sequence numbers entirely, so clients and servers talk only in permanent UIDs. RFC 9738 IMAP MESSAGELIMIT IMAP MESSAGELIMIT Extension A way for an IMAP server to announce how many messages one command may touch, so clients can work in batches. RFC 2088 IMAP4 Literal+ IMAP4 non-synchronizing literals An IMAP literal form that lets a client send data without waiting for a continuation request. RFC 1138 X.400 and RFC 822 Mapping between X.400(1988) / ISO 10021 and RFC 822 A rulebook for gateways that translate mail between X.400 (1988) systems and Internet RFC 822 mail. RFC 5750 S/MIME 3.2 Certs Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.2 Certificate Handling How mail programs check and use digital ID certificates for secure email. RFC 6855 IMAP Support for UTF-8 International characters in email servers and addresses RFC 2425 MIME Directory A MIME Content-Type for Directory Information A standard text format for structuring directory information in email messages. RFC 2476 Mail Submission Message Submission Why email clients should hand new messages to a dedicated submission server on port 587, and what that server should do. RFC 1590 Media Type Registration Media Type Registration Procedure How new MIME media types get registered with IANA, and why the original rules were loosened. RFC 1652 8BITMIME SMTP Service Extension for 8bit-MIMEtransport How two mail servers agree to pass message bodies that use 8-bit characters, not just 7-bit ASCII. RFC 1730 IMAP4 Internet Message Access Protocol - Version 4 Protocol for accessing and managing email messages on a server. RFC 1734 POP3 AUTH POP3 AUTHentication command An optional POP3 command for choosing an authentication mechanism. RFC 1891 SMTP DSN Extension SMTP Service Extension for Delivery Status Notifications Let email senders request delivery status notifications under chosen conditions. RFC 2554 SMTP AUTH SMTP Service Extension for Authentication Letting mail clients prove their identity to the mail server before sending mail. RFC 7601 Authentication-Results Message Header Field for Indicating Message Authentication Status A header that tells mail software which authentication checks a message passed, such as SPF and DKIM. RFC 2305 Simple Mode Fax A Simple Mode of Facsimile Using Internet Mail Sending fax documents over Internet mail using TIFF format. RFC 1113 PEM Part I Privacy enhancement for Internet electronic mail: Part I - message encipherment and authentication procedures How to encrypt and authenticate Internet electronic mail so recipients know the message is real and unopened. RFC 1225 POP3 Post Office Protocol: Version 3 How lightweight workstations retrieve mail from a server without running their own mail system. RFC 2112 Multipart/Related The MIME Multipart/Related Content-type A standard way to send related documents together, like HTML with its images. RFC 5336 SMTPUTF8 SMTP Extension for Internationalized Email Addresses Sending email with addresses and text written in any alphabet. RFC 5335 Internationalized Email Headers UTF-8 characters in email headers instead of ASCII encoding RFC 453 Meeting announcement to discuss a network mail system An announcement of a meeting to discuss how network mail should work. RFC 510 Request for network mailbox addresses A request for mailbox details so the NIC could deliver its Network Journal by network mail. RFC 539 Thoughts on the mail protocol proposed in RFC 524 Crocker and Postel's review of the mail protocol proposed in RFC 524. RFC 706 On the junk mail problem A short proposal for refusing unwanted messages at the Host/IMP interface. RFC 757 Suggested solution to the naming, addressing, and delivery problem for ARPANET message systems A request for comments on separating a mail recipient's identity from delivery addresses. RFC 784 Mail Transfer Protocol: ISI TOPS20 implementation How ISI organized an MTP mail implementation for TOPS-20 systems. RFC 805 Computer mail meeting notes How the Internet settled on hierarchical domain-based email addresses RFC 1137 822 Restricted Mapping Mapping between full RFC 822 and RFC 822 with restricted encoding A reversible mapping for RFC 822 addresses crossing systems with restricted character sets. RFC 1648 Postmaster Convention for X.400 Operations A convention for supporting postmaster addresses in mapped X.400 mail domains. RFC 2159 A MIME Body Part for FAX How to carry a Group 3 fax inside a MIME email message, and map it to and from X.400. RFC 2221 IMAP4 Login Referrals IMAP4 Login Referrals How an IMAP4 server can direct a client to the server holding a user's mailboxes. RFC 2312 S/MIME v2 Certificates S/MIME Version 2 Certificate Handling How S/MIME version 2 mail programs create, check and manage X.509 certificates. RFC 2384 POP URL POP URL Scheme A way to write the address of a POP mailbox as a link, with the server, port and login method in one string. RFC 2645 ODMR ON-DEMAND MAIL RELAY (ODMR) SMTP with Dynamic IP Addresses How a mail server with a changing IP address can call its provider and ask for the mail waiting for it. RFC 4095 Solicitation Keywords Attaching Meaning to Solicitation Class Keywords How to turn a reversed-domain spam label into a web page that explains what the label means. RFC 4356 MMS to Email Mapping Mapping Between the Multimedia Messaging Service (MMS) and Internet Mail How a phone's multimedia messages are translated to and from ordinary Internet email, header by header. RFC 5032 IMAP WITHIN WITHIN Search Extension to the IMAP Protocol Two IMAP search keys that match mail by its age in seconds. RFC 5260 Sieve Date and Index Sieve Email Filtering: Date and Index Extensions Two Sieve extensions: test dates and times in mail filters, and pick which copy of a repeated header to test. RFC 5463 Sieve ihave Sieve Email Filtering: Ihave Extension Lets a Sieve mail filter script use optional extensions only when they are available, and fail cleanly when they are not. RFC 5466 IMAP Filters IMAP4 Extension for Named Searches (Filters) Save a favorite IMAP search on the server under a name, then reuse it by name in later searches. RFC 5524 URLFETCH binary Extended URLFETCH for Binary and Converted Parts Lets IMAP URLFETCH return decoded content and type metadata for a message part, not just the raw encoded bytes. RFC 5784 Sieve XML Sieve Email Filtering: Sieves and Display Directives in XML A way to write Sieve mail filters as XML, plus extra elements that let graphical editors group and label rules. RFC 6008 Auth-Results header.b Authentication-Results Registration for Differentiating among Cryptographic Results A small registry addition that lets a mail checker say which DKIM signature each result belongs to. RFC 6009 Sieve Email Filtering: Delivery Status Notifications and Deliver-By Extensions Lets a Sieve mail filter read and set delivery-notification and delivery-deadline settings on the message envelope. RFC 6212 VBR results Authentication-Results Registration for Vouch by Reference Results A small registry update that lets a mail system record the outcome of a Vouch By Reference check in a message header. RFC 6430 ARF not-spam Email Feedback Report Type Value: not-spam A new feedback report type that lets a mail user say a message was wrongly marked as spam. RFC 6468 Sieve SIP notification Sieve Notification Mechanism: SIP MESSAGE How a Sieve mail filter can tell you about new mail by sending a SIP instant message. RFC 6558 Sieve CONVERT Sieve Extension for Converting Messages before Delivery A Sieve action and test that converts message attachments, such as shrinking images, before delivery. RFC 6647 Email Greylisting Email Greylisting: An Applicability Statement for SMTP How and why mail servers temporarily turn away unknown senders, and what it costs legitimate mail. RFC 6729 Email handling states Indicating Email Handling States in Trace Fields A small addition to the Received header that says when an email was put aside, and why. RFC 7293 RRVS The Require-Recipient-Valid-Since Header Field and SMTP Service Extension A way for a sender to say "I knew who owned this mailbox at this time", so mail is not delivered to a later owner. RFC 7352 Sieve duplicate Sieve Email Filtering: Detecting Duplicate Deliveries A Sieve test that lets an email filter notice it has already seen a message and handle the copy. RFC 8437 IMAP UNAUTHENTICATE IMAP UNAUTHENTICATE Extension for Connection Reuse A new IMAP command that lets an administrative client switch users without hanging up and reconnecting. RFC 8438 IMAP STATUS=SIZE IMAP Extension for STATUS=SIZE Ask an IMAP server for the total size of a mailbox with one STATUS command. RFC 8440 IMAP LIST-MYRIGHTS IMAP4 Extension for Returning MYRIGHTS Information in Extended LIST One IMAP LIST command can now return each mailbox together with the rights you hold on it. RFC 8508 IMAP REPLACE IMAP REPLACE Extension An IMAP command that swaps one stored message for a new one in a single step, built for saving drafts as you type. RFC 8514 IMAP SAVEDATE Internet Message Access Protocol (IMAP) - SAVEDATE Extension An IMAP extension that adds a save date: the moment a message landed in its current mailbox, which cannot be faked or copied. RFC 8689 SMTP REQUIRETLS SMTP Require TLS Option Lets an email sender demand encrypted, authenticated delivery, or explicitly waive it, one message at a time. RFC 8887 JMAP over WebSocket A JSON Meta Application Protocol (JMAP) Subprotocol for WebSocket How JMAP clients and servers can keep one authenticated WebSocket open instead of authenticating every HTTP request. RFC 8970 IMAP PREVIEW IMAP4 Extension: Message Preview Generation Lets an IMAP mail client ask the server for a short, ready-made text preview of each message. RFC 9219 S/MIME Signature Verification Extension to the JSON Meta Application Protocol (JMAP) Lets a JMAP mail server tell your mail client whether an S/MIME signature checked out, so the client does not have to. RFC 9422 SMTP LIMITS The LIMITS SMTP Service Extension How a mail server tells a client its limits up front, in the reply to EHLO, so the client stops tripping over them. RFC 9585 IMAP INPROGRESS IMAP Response Code for Command Progress Notifications A standard way for an IMAP server to tell a client how far along a slow command is, or just that it is still alive. RFC 9590 IMAP LIST-METADATA IMAP Extension for Returning Mailbox METADATA in Extended LIS Lets an email client ask for folder list and per-folder annotations in one IMAP command. RFC 9661 JMAP for Sieve The JSON Meta Application Protocol (JMAP) for Sieve Scripts How a JMAP client lists, uploads, activates and validates email-filtering Sieve scripts on a server. RFC 9698 IMAP JMAPACCESS The JMAPACCESS Extension for IMAP An IMAP extension that tells a logged-in client the same mail is also reachable through JMAP, and where. RFC 9749 JMAP Web Push VAPID Use of Voluntary Application Server Identification (VAPID) in JSON Meta Application Protocol (JMAP) Web Push How JMAP clients discover and use a server's VAPID key for Web Push. RFC 1342 MIME Header Encoding Representation of Non-ASCII Text in Internet Message Headers Encoding non-ASCII characters in email headers using a printable ASCII wrapper. RFC 1426 8BITMIME SMTP Service Extension for 8bit-MIMEtransport Lets mail servers send messages with non-ASCII characters without encoding. RFC 2086 IMAP4 ACL IMAP4 ACL extension Control who can access shared mailboxes through IMAP. RFC 2087 IMAP4 QUOTA IMAP4 QUOTA extension An IMAP extension for reporting and managing mailbox resource limits. RFC 2184 MIME Parameter Value and Encoded Word Extensions: Character Sets, Languages, and Continuations Extending MIME to handle character sets, languages, and long parameter values. RFC 2304 Minimal FAX address format in Internet Mail A standard format for putting fax numbers in email addresses. RFC 788 SMTP Simple Mail Transfer Protocol A command-and-reply protocol for transferring mail between hosts. RFC 1148 X.400 and RFC 822 Mapping between X.400(1988) / ISO 10021 and RFC 822 How to translate between two incompatible email systems at a gateway. RFC 1528 Principles of Operation for the TPC.INT Subdomain: Remote Printing -- Technical Procedures Using email to send documents for remote printing via facsimile machines. RFC 1725 POP3 Post Office Protocol - Version 3 How a small computer fetches its waiting email from a server, one session at a time. RFC 1806 Content-Disposition Communicating Presentation Information in Internet Messages: The Content-Disposition Header A header that tells email clients whether to show message parts inline or as downloadable attachments. RFC 2197 SMTP Pipelining SMTP Service Extension for Command Pipelining A faster way to send mail by bundling commands together RFC 2423 VPIM Voice Message MIME Sub-type Registration A MIME label to mark messages as voice mail. RFC 5337 Internationalized Delivery Status and Disposition Notifications Delivery status notifications that preserve non-ASCII email addresses. RFC 5504 UTF8SMTP downgrade Downgrading Mechanism for Email Address Internationalization Converting internationalized emails to ASCII when crossing non-UTF8-capable mail servers RFC 1563 text/enriched The text/enriched MIME Content-type Simple formatting markup for email that works on any system. RFC 1114 PEM Part II Privacy enhancement for Internet electronic mail: Part II - certificate-based key management How to issue and trust encryption keys for secure email RFC 1854 SMTP Pipelining SMTP Service Extension for Command Pipelining Send multiple email commands at once instead of waiting for each reply. RFC 2303 Minimal PSTN address format in Internet Mail How to write a phone number as an email address for gateways RFC 2487 STARTTLS for SMTP SMTP Service Extension for Secure SMTP over TLS Upgrade SMTP connections to encryption mid-conversation. RFC 2632 S/MIME v3 Certificates S/MIME Version 3 Certificate Handling How S/MIME version 3 uses PKIX certificates to secure email messages and verify senders. RFC 2646 format=flowed The Text/Plain Format Parameter A way to write email that adapts to different screen widths. RFC 4550 Lemonade profile Internet Email to Support Diverse Service Environments (Lemonade) Profile A profile of IMAP and SMTP for clients with limited resources to send and receive email. RFC 5162 IMAP QRESYNC IMAP4 Extensions for Quick Mailbox Resynchronization Quickly resync a mailbox after disconnection without extra round trips. RFC 5672 DKIM identifier update RFC 4871 DomainKeys Identified Mail (DKIM) Signatures -- Update Clarify what DKIM signatures tell you about who sent an email. RFC 5788 IMAP Keyword Registry IMAP4 Keyword Registry A registry and a registration process for the flags IMAP clients put on email messages. RFC 1460 POP3 Post Office Protocol - Version 3 A simple protocol for a mail client to pick up and delete the mail waiting for it on a server. RFC 1653 SMTP SIZE SMTP Service Extension for Message Size Declaration How an SMTP client can announce a message's size up front so the server can say no before the data is sent. RFC 1911 VPIM Voice Profile for Internet Mail A standard way for voice mail systems from different manufacturers to exchange messages using Internet email. RFC 2249 Mail Monitoring MIB A standardized way to monitor mail servers using SNMP. RFC 2422 ADPCM MIME Type Toll Quality Voice - 32 kbit/s ADPCM MIME Sub-type Registration A standardized MIME type for sending compressed voice audio in email. RFC 1115 PEM Part III Privacy enhancement for Internet electronic mail: Part III - algorithms, modes, and identifiers Algorithm identifiers and specifications for Privacy Enhanced Mail. RFC 1566 Mail Monitoring MIB Monitoring message delivery systems with SNMP gauges and counters RFC 2095 IMAP/POP AUTHorize IMAP/POP AUTHorize Extension for Simple Challenge/Response A keyed-MD5 challenge-response authentication mechanism for IMAP and POP. RFC 2302 image/tiff Tag Image File Format (TIFF) - image/tiff MIME Sub-type Registration The standard MIME type for TIFF images sent over email and web protocols. RFC 3009 parityfec MIME types Registration of parityfec MIME types Names for forward error correction streams in RTP RFC 3250 Tag Image File Format Fax eXtended (TIFF-FX) - image/tiff-fx MIME Sub-type Registration Official registration of a MIME type for fax images in TIFF-FX format. RFC 3431 Sieve relational Sieve Extension: Relational Tests Add comparison operators to the Sieve mail filtering language. RFC 3598 Sieve Subaddress Sieve Email Filtering -- Subaddress Extension Filter email by examining the user and detail parts of plus-addressed mailboxes. RFC 6577 Auth-Results SPF Update Authentication-Results Registration Update for Sender Policy Framework (SPF) Results Aligns an Authentication-Results SPF result with the SPF specification. RFC 780 MTP Mail Transfer Protocol A mail transfer protocol with relaying and two optional multi-recipient schemes. RFC 1486 Remote printing An Experiment in Remote Printing Using Internet email to send print jobs to fax machines by telephone number. RFC 1642 UTF-7 UTF-7 - A Mail-Safe Transformation Format of Unicode Encoding Unicode in 7-bit ASCII for email and old systems RFC 5248 A Registry for SMTP Enhanced Mail System Status Codes An IANA registry so that new SMTP enhanced status codes stop colliding with each other. RFC 4870 DomainKeys Domain-Based Email Authentication Using Public Keys Advertised in the DNS (DomainKeys) Sign email with public keys published in the DNS to prove it came from a domain. RFC 993 PCMAIL PCMAIL: A distributed mail system for personal computers A distributed mail system for personal computers with central storage and multiple client workstations. RFC 7817 Email TLS Identity Check Updated Transport Layer Security (TLS) Server Identity Check Procedure for Email-Related Protocols One consistent rule for how email clients decide that the server behind a TLS connection is really the one they meant to reach. RFC 772 MTP Mail Transfer Protocol A draft protocol for sending mail between network hosts RFC 989 PEM Privacy enhancement for Internet electronic mail: Part I: Message encipherment and authentication procedures The first Privacy-Enhanced Mail RFC: end-to-end encryption and sender authentication for Internet email, with no changes to mail relays. RFC 1081 POP3 Post Office Protocol: Version 3 A protocol for workstations to retrieve mail from a server. RFC 1427 SMTP SIZE SMTP Service Extension for Message Size Declaration Lets clients declare message size so servers can reject too-large messages before they arrive. RFC 1544 Content-MD5 The Content-MD5 Header Field An optional MIME header for checking that decoded content was not accidentally changed RFC 2110 MHTML MIME E-mail Encapsulation of Aggregate Documents, such as HTML (MHTML) How to send web pages with pictures in email. RFC 2359 IMAP UIDPLUS IMAP4 UIDPLUS extension Three protocol optimizations that let email clients work more efficiently with IMAP servers. RFC 2424 Content Duration MIME Header Definition A MIME field that states the playback duration of timed media. RFC 3685 Sieve spamtest SIEVE Email Filtering: Spamtest and VirusTest Extensions Portable spam and virus scoring tests for email filters. RFC 155 ARPA Network mailing lists The people and addresses for distributing early network documents RFC 168 ARPA Network mailing lists Three postal mailing lists for distributing early network documents RFC 221 Mail Box Protocol: Version 2 A proposal for appending network messages to a site's mail box RFC 329 ARPA Network Mailing Lists Three postal mailing lists for distributing network documents in May 1972 RFC 363 ARPA Network mailing lists Three revised mailing lists for distributing ARPANET documents RFC 1830 SMTP Large and Binary SMTP Service Extensions for Transmission of Large and Binary MIME Messages Send large emails and binary attachments without encoding overhead. RFC 5738 IMAP UTF-8 IMAP Support for UTF-8 Extending IMAP to handle UTF-8 in usernames, mailbox names, and message headers RFC 6237 IMAP multimailbox SEARCH IMAP4 Multimailbox SEARCH Extension Search multiple mailboxes with a single command RFC 1168 Intermail Intermail and Commercial Mail Relay services Bridging electronic mail between the Internet and commercial systems. RFC 1211 Problems with the maintenance of large mailing lists What running the IETF mailing lists taught ISI about bounced mail, sublists and misdirected requests. RFC 1343 A User Agent Configuration Mechanism for Multimedia Mail Format Information A shared configuration file format that tells all mail clients which programs should handle which types of attachments. RFC 1344 Implications of MIME for Internet Mail Gateways How mail gateways can take advantage of MIME to improve service RFC 1429 LISTSERV Listserv Distribute Protocol A protocol for bulk email delivery to large mailing lists RFC 1616 X.400(1988) for the Academic and Research Community in Europe A plan for deploying next-generation email across European research institutions. RFC 1711 Classifications in E-mail Routing A taxonomy of email routing strategies for distributed mail systems RFC 1741 BinHex MIME MIME Content Type for BinHex Encoded Files How to send Macintosh files as MIME email attachments using BinHex 4.0 encoding. RFC 1802 Project Long Bud Introducing Project Long Bud: Internet Pilot Project for the Deployment of X.500 Directory Information in Support of X.400 Routing A test run using X.500 directories to route X.400 email across the Internet. RFC 1895 CALS-1840 Content-type The Application/CALS-1840 Content-type Mailing military technical documents through email RFC 1927 Joke MIME Types Suggested Additional MIME Types for Associating Documents An April 1st parody that imagines electronic staples and paper clips for documents. RFC 1947 Greek Email Encoding Greek Character Encoding for Electronic Mail Messages How to send email with Greek text and ensure it arrives correctly. RFC 1957 Some Observations on Implementations of the Post Office Protocol (POP3) Implementation observations about POP3 server and client behavior. RFC 2442 Batch SMTP The Batch SMTP Media Type Encapsulate SMTP transactions as MIME objects for transport through non-SMTP networks. RFC 2503 MIME Types for Use with the ISO ILL Protocol A standard way to send library loan request forms by email RFC 2524 EMSD Neda's Efficient Mail Submission and Delivery (EMSD) Protocol Specification Version 1.3 Efficient mail submission and delivery for wireless and bandwidth-limited networks. RFC 2635 DON'T SPEW DON'T SPEW A Set of Guidelines for Mass Unsolicited Mailings and Postings (spam*) Why mass unsolicited email harms the Internet and how to handle it. RFC 2927 MIME Directory Profile for LDAP Schema A way to package LDAP schema definitions as email attachments. RFC 3073 Portable Font Resource (PFR) - application/font-tdpfr MIME Sub-type Registration Registers the MIME type for Portable Font Resource files. RFC 3240 DICOM MIME Type Digital Imaging and Communications in Medicine (DICOM) - Application/dicom MIME Sub-type Registration Registers the application/dicom media type for medical imaging data. RFC 3249 Implementers Guide for Facsimile Using Internet Mail Practical fixes and cautions for anyone building software that sends faxes over Internet mail. RFC 3391 PWG multiplexed type The MIME Application/Vnd.pwg-multiplexed Content-Type A MIME type for packaging multi-component documents with interleaved parts RFC 3974 SMTP Operational Experience in Mixed IPv4/v6 Environments Keeping mail flowing when DNS has both old and new address formats. RFC 4047 FITS MIME Types MIME Sub-type Registrations for Flexible Image Transport System (FITS) Registering standard media types for astronomical data files RFC 4096 Email Subject Labels Policy-Mandated Labels Such as "Adv:" in Email Subject Headers Considered Ineffective At Best Why policy-mandated labels like Adv: in email subject lines don't work and what to do instead. RFC 4249 Implementer-Friendly Specification of Message and MIME-Part Header Fields and Field Components Guide for writing clear email header field specifications. RFC 4416 LEMONADE Goals Goals for Internet Messaging to Support Diverse Service Environments Design principles for mobile email across phones, networks, and media types RFC 4902 Integrity, Privacy, and Security in Open Pluggable Edge Services (OPES) for SMTP Applying Open Pluggable Edge Services to email and SMTP gateways. RFC 5551 Lemonade notifications Lemonade Notifications Architecture How email systems can tell phones and other constrained clients that something interesting happened, without constant polling. RFC 5616 IMAP streaming Streaming Internet Messaging Attachments Stream audio and video email attachments instead of downloading them fully. RFC 6109 Italian PEC La Posta Elettronica Certificata - Italian Certified Electronic Mail A government-backed certified email system with legal proof of delivery RFC 6133 Sieve Auto-Responder Sieve Email Filtering: Use of Presence Information with Auto-Responder Functionality Using email filtering rules to send smart automatic replies based on presence and address book. RFC 6471 DNSBL best practices Overview of Best Email DNS-Based List (DNSBL) Operational Practices How to run and use DNS-based blocklists for email reputation RFC 6477 MMHS header fields Registration of Military Message Handling System (MMHS) Header Fields for Use in Internet Mail Header fields for military message services in Internet email. RFC 6686 SPF and Sender ID Resolution of the Sender Policy Framework (SPF) and Sender ID Experiments A report card on SPF and Sender ID: after six years of surveys, SPF won and the experiments were declared concluded. RFC 6758 MT-PRIORITY tunneling Tunneling of SMTP Message Transfer Priorities How to preserve email priority through mail servers that don't understand priority. RFC 7017 IMAP Access to IETF Email List Archives Requirements for browsing and searching IETF mailing-list archives with IMAP clients. RFC 7103 Advice for Safe Handling of Malformed Messages Practical guidance for handling email messages that don't follow the rules. RFC 7259 Jabber-ID Header The Jabber-ID Header Field Add your XMPP chat address to an email message header. RFC 7281 Authentication-Results Registration for S/MIME Signature Verification Reporting S/MIME signature verification results in email headers RFC 7444 SIO-Label Security Labels in Internet Email A header field to mark email messages with sensitivity information for display and policy handling. RFC 7681 Email Exchange of Secondary School Transcripts A secure way for students to email their school transcripts to colleges and employers RFC 7912 Message Authorizing Email Header Field and Its Use for the Draft and Release Procedure A header field for military message approval and secure release RFC 8494 MULE Multicast Email (MULE) over Allied Communications Publication (ACP) 142 Send email to many receivers at once over bandwidth-limited radio networks. RFC 8904 DNSWL DNS Whitelist (DNSWL) Email Authentication Method Extension Recording whether a sender's IP address is on a trusted whitelist. RFC 9979 IMAP/JMAP keywords Registration of Further IMAP/JMAP Keywords and Mailbox Name Attributes Standardized labels for email features that were already in wide use RFC 196 Mail Box Protocol A proposal for sending sequential files to a site's network mailbox. RFC 724 Proposed official standard for the format of ARPA Network messages A proposal to standardize the format of ARPA Network messages. RFC 984 PCMAIL PCMAIL: A distributed mail system for personal computers A distributed mail system architecture for personal computers with a central repository RFC 1064 IMAP2 Interactive Mail Access Protocol: Version 2 A protocol for workstations to access mail stored on a remote server. RFC 5008 Suite B S/MIME Suite B in Secure/Multipurpose Internet Mail Extensions (S/MIME) Using NSA-approved cryptography for secure email RFC 1529 Principles of Operation for the TPC.INT Subdomain: Remote Printing -- Administrative Policies Administrative policies for remote printer servers in the tpc.int subdomain. RFC 1523 text/enriched The text/enriched MIME Content-type A simple format for sending formatted text in emails. RFC 1569 Principles of Operation for the TPC.INT Subdomain: Radio Paging -- Technical Procedures Using Internet email to send pages to radio pagers via phone numbers. RFC 1820 MIME UA Checklist Multimedia E-mail (MIME) User Agent Checklist A to-do list for testing whether an email client can handle multimedia attachments. RFC 9122 Sieve Actions Registry IANA Registry for Sieve Actions A new IANA registry that lists every Sieve mail-filtering action and how it interacts with the others. RFC 1040 PEM Privacy enhancement for Internet electronic mail: Part I: Message encipherment and authentication procedures The first part of a privacy enhancement system for email that encrypts and authenticates messages. RFC 1154 Encoding Header Encoding header field for internet messages A header field for describing multi-part email messages and how to decode each part. RFC 1405 X.400 to Mail-11 Mapping between X.400(1984/1988) and Mail-11 (DECnet mail) How to translate messages between two different email systems RFC 5721 POP3 UTF-8 POP3 Support for UTF-8 Bringing international characters to the email retrieval protocol. RFC 5825 Downgraded EAI Display Displaying Downgraded Messages for Email Address Internationalization Showing international email addresses after they've been converted to ASCII. RFC 5983 Mailing Lists and Internationalized Email Addresses Handling international addresses in mailing list operations RFC 9091 DMARC PSD Experimental Domain-Based Message Authentication, Reporting, and Conformance (DMARC) Extension for Public Suffix Domains Extending DMARC policy to top-level and multi-part domains RFC 3462 multipart/report The Multipart/Report Content Type for the Reporting of Mail System Administrative Messages A container for email reports mixing human and machine readable content. RFC 806 Proposed Federal Information Processing Standard: Specification for message format for computer based message systems A standard format for messages between different mail systems so they can understand each other. RFC 918 POP Post Office Protocol A TCP protocol for a workstation to retrieve mail from a mailbox server. RFC 1153 Digest Format Digest message format A format for combining mailing-list messages into a single digest. RFC 1204 MPP Message Posting Protocol (MPP) Protocol for personal computers to submit outgoing mail to a mail service host. RFC 1339 RMCP Remote Mail Checking Protocol Lightweight UDP-based protocol for checking if new mail has arrived. RFC 1845 SMTP Checkpoint/Restart SMTP Service Extension for Checkpoint/Restart Resume interrupted mail transfers without resending everything that arrived before the break. RFC 3183 Domain Security Services using S/MIME S/MIME security services at the domain boundary, not end-to-end. RFC 6541 DomainKeys Identified Mail (DKIM) Authorized Third-Party Signatures Authorizing third-party services to sign email with DKIM on a domain's behalf RFC 7508 Secure Headers Securing Header Fields with S/MIME Protecting email message headers with cryptographic signatures and encryption. RFC 8617 ARC The Authenticated Received Chain (ARC) Protocol A chain of signed header fields that lets each mail handler record what authentication checks the message passed. RFC 9057 Author header field Email Author Header Field Preserving the original author when mailing lists modify the From field RFC 9078 Email Reaction Reaction: Indicating Summary Reaction to a Message Bringing social media style reactions to email messages RFC 9228 Delivered-To Delivered-To Email Header Field Email header field to record delivery addresses RFC 9477 CFBL address header Complaint Feedback Loop Address Header Automated feedback loop for email spam complaints without manual setup. RFC 1892 Multipart/Report The Multipart/Report Content Type for the Reporting of Mail System Administrative Messages A MIME container for human-readable and machine-readable mail reports. RFC 7114 Creation of a Registry for smime-type Parameter Values Creates an IANA registry for S/MIME smime-type parameter values. RFC 7107 Object Identifier Registry for the S/MIME Mail Security Working Group Who holds the S/MIME object identifier arc, what is already numbered inside it, and how new numbers get handed out. RFC 1872 MIME Multipart/Related The MIME Multipart/Related Content-type A MIME content-type for sending related parts that make sense only together. RFC 224 Comments on Mailbox Protocol Why a Terminal IMP needed a remote host to store and serve mail. RFC 456 Memorandum: Date change of mail meeting A revised date for the Network Mail meeting announced in RFC 453. RFC 458 FTP Mail retrieval via FTP Two proposed FTP commands for reading mail stored at another site. RFC 469 Network mail meeting summary The NIC's summary of conclusions from the Network Mail meeting. RFC 498 On mail service to CCN UCLA-CCN's mail practices and proposed FTP mail extensions. RFC 574 Announcement of a Mail Facility at UCSB An announcement of UCSB's network mail service. RFC 577 Mail priority An argument for carrying sender-assigned urgency in mail. RFC 720 Address Specification Syntax for Network Mail A proposed syntax that separates personal names, user IDs, mailboxes, and hosts. RFC 751 Survey of FTP mail and MLFL A survey of how ARPANET FTP servers handled unknown recipients and the MLFL command. RFC 754 Out-of-net host addresses for mail Four short-term ways to address mail to users outside the ARPANET. RFC 763 Role mailboxes A suggestion to use mail aliases for official roles rather than named individuals. RFC 771 Mail transition plan A plan for keeping mail working while switching from ARPANET to Internet protocols. RFC 773 Comments on NCP/TCP mail service transition strategy Comments on keeping mail working during a transition from NCP to TCP. RFC 786 Mail Transfer Protocol: ISI TOPS20 MTP-NIMAIL interface The file interface between MTP and NIMAIL on ISI TOPS-20. RFC 807 Multimedia mail meeting notes Meeting notes on connecting computers to send mixed-type messages in 1982. RFC 808 Summary of computer mail services meeting held at BBN on 10 January 1979 Summary of a 1979 meeting on unifying the chaotic state of ARPANET email. RFC 876 SMTP survey Survey of SMTP implementations A 1983 snapshot of how the Internet's mail servers handled the new protocol. RFC 886 Proposed standard for message header munging Rules for translating mail between systems with different message formats. RFC 910 Multimedia mail meeting notes Meeting notes on early multimedia email systems, 1984 RFC 915 Network mail path service A network service to find mail routes to non-Internet hosts. RFC 1082 POP3 Extensions Post Office Protocol: Version 3: Extended service offerings Add discussion group mailbox access to POP3 so one client can read both personal mail and shared group messages.