The following IETF specifications define the IMAP, POP3 and SMTP protocols:
- 821: SIMPLE MAIL TRANSFER PROTOCOL
- 822: STANDARD FOR THE FORMAT OF ARPA INTERNET TEXT MESSAGES
- 974: MAIL ROUTING AND THE DOMAIN SYSTEM
- 1081: Post Office Protocol - Version 3
- 1123: Requirements for Internet Hosts -- Application and Support
- 1225: Post Office Protocol - Version 3 (Obsoletes rfc1081)
- 1425: SMTP Service Extensions
- 1426: SMTP Service Extension for 8bit-MIME transport
- 1460: Post Office Protocol - Version 3 (Obsoletes rfc1225)
- 1651: SMTP Service Extensions (Obsoletes rfc1425)
- 1652: SMTP Service Extension for 8bit-MIME transport (Obsoletes rfc1426)
- 1653: SMTP Service Extension for Message Size Declaration
- 1725: Post Office Protocol - Version 3 (Obsoletes rfc1460)
- 1730: INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4
- 1731: IMAP4 Authentication Mechanisms
- 1734: POP3 AUTHentication command
- 1830: SMTP Service Extensions for Transmission of Large and Binary MIME Messages
- 1854: SMTP Service Extension for Command Pipelining
- 1870: SMTP Service Extension for Message Size Declaration (Obsoletes rfc1653)
- 1869: SMTP Service Extensions
- 1891: SMTP Service Extension for Delivery Status Notifications
- 1928: SOCKS Protocol Version 5
- 1929: Username/Password Authentication for SOCKS V5
- 1939: Post Office Protocol - Version 3 (Obsoletes rfc1725)
- 1961: GSS-API Authentication Method for SOCKS Version 5
- 2034: SMTP Service Extension for Returning Enhanced Error Codes
- 2060: INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1 (Obsoletes rfc1730)
- 2086: IMAP4 ACL extension
- 2087: IMAP4 QUOTA extension
- 2088: IMAP4 non-synchronizing literals
- 2095: IMAP/POP AUTHorize Extension for Simple Challenge/Response
- 2177: IMAP4 IDLE command
- 2193: IMAP4 Mailbox Referrals
- 2195: IMAP/POP AUTHorize Extension for Simple Challenge/Response (Obsoletes rfc2095)
- 2197: SMTP Service Extension for Command Pipelining (Obsoletes rfc1854)
- 2221: IMAP4 Login Referrals
- 2222: Simple Authentication and Security Layer (SASL)
- 2245: Anonymous SASL Mechanism
- 2342: IMAP4 Namespace
- 2359: IMAP4 UIDPLUS extension
- 2449: POP3 Extension Mechanism (Updates rfc1939)
- 2487: SMTP Service Extension for Secure SMTP over TLS
- 2554: SMTP Service Extension for Authentication
- 2595: Using TLS with IMAP, POP3 and ACAP
- 2683: IMAP4 Implementation Recommendations
- 2821: Simple Mail Transfer Protocol (Obsoletes rfc0821, rfc0974, rfc1869) (Updates rfc1123)
- 2822: Internet Message Format (Obsoletes rfc0822)
- 2831: Using Digest Authentication as a SASL Mechanism
- 2920: SMTP Service Extension for Command Pipelining (Obsoletes rfc2197)
- 2971: IMAP4 ID extension
- 3030: SMTP Service Extensions for Transmission of Large and Binary MIME Messages (Obsoletes rfc1830)
- 3207: SMTP Service Extension for Secure SMTP over Transport Layer Security (Obsoletes rfc2487)
- 3348: The Internet Message Action Protocol (IMAP4) Child Mailbox Extension
- 3461: Simple Mail Transfer Protocol (SMTP) Service Extension for Delivery Status Notifications (DSNs) (Obsoletes rfc1891)
- 3501: INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1 (Obsoletes rfc2060)
- 3502: Internet Message Access Protocol (IMAP) - MULTIAPPEND Extension
- 3516: IMAP4 Binary Content Extension
- 3691: Handle System Namespace and Service Definition
- 4013: SASLprep: Stringprep Profile for User Names and Passwords
- 4314: IMAP4 Access Control List (ACL) Extension (Obsoletes rfc2086)
- 4315: Internet Message Access Protocol (IMAP) - UIDPLUS extension (Obsoletes rfc2359)
- 4466: Collected Extensions to IMAP4 ABNF (Updates rfc2088, rfc2342, rfc3501, rfc3502, rfc3516)
- 4469: Internet Message Access Protocol (IMAP) CATENATE Extension (Updates rfc3501, rfc3502)
- 4505: Anonymous Simple Authentication and Security Layer (SASL) Mechanism (Obsoletes rfc2245)
- 4551: IMAP Extension for Conditional STORE Operation or Quick Flag Changes Resynchronization (Updates rfc3501)
- 4616: The PLAIN Simple Authentication and Security Layer (SASL) Mechanism (Updates rfc2595)
- 4731: IMAP4 Extension to SEARCH Command for Controlling What Kind of Information Is Returned
- 4952: Overview and Framework for Internationalized Email
- 4959: IMAP Extension for Simple Authentication and Security Layer (SASL) Initial Client Response
- 4978: The IMAP COMPRESS Extension
- 5032: WITHIN Search Extension to the IMAP Protocol (Updates rfc3501)
- 5161: The IMAP ENABLE Extension
- 5162: IMAP4 Extensions for Quick Mailbox Resynchronization
- 5182: IMAP Extension for Referencing the Last SEARCH Result (Updates rfc3501)
- 5255: Internet Message Access Protocol Internationalization
- 5256: Internet Message Access Protocol - SORT and THREAD Extensions
- 5257: Internet Message Access Protocol - ANNOTATE Extension
- 5258: Internet Message Access Protocol version 4 - LIST Command Extensions (Obsoletes rfc3348) (Updates rfc2193)
- 5259: Internet Message Access Protocol - CONVERT Extension
- 5267: Contexts for IMAP4
- 5321: Simple Mail Transfer Protocol (Obsoletes rfc2821) (Updates rfc1123)
- 5336: SMTP Extension for Internationalized Email Addresses (Updates rfc2821, rfc2822, rfc4952)
- 5464: The IMAP METADATA Extension
- 5465: The IMAP NOTIFY Extension (Updates rfc5267)
- 5466: IMAP4 Extension for Named Searches (Filters)
- 5530: IMAP Response Codes
- 5721: POP3 Support for UTF-8
- 5738: IMAP Support for UTF-8 (Updates rfc3501)
- 5788: IMAP4 Keyword Registry
- 5801: Using Generic Security Service Application Program Interface (GSS-API) Mechanisms in Simple Authentication and Security Layer (SASL): The GS2 Mechanism Family
- 5802: Salted Challenge Response Authentication Mechanism (SCRAM) SASL and GSS-API Mechanisms
- 5819: IMAP4 Extension for Returning STATUS Information in Extended LIST
- 5957: Display-Based Address Sorting for the IMAP4 SORT Extension (Updates rfc5256)
- 6154: IMAP LIST Extension for Special-Use Mailboxes
- 6203: IMAP4 Extension for Fuzzy Search
- 6237: IMAP4 Multimailbox SEARCH Extension (Obsoletes rfc4466)
- 6531: SMTP Extension for Internationalized Email (Obsoletes rfc5336)
- 6851: Internet Message Access Protocol (IMAP) - MOVE Extension
- 6855: IMAP Support for UTF-8 (Obsoletes rfc5738)
- 6856: Post Office Protocol Version 3 (POP3) Support for UTF-8 (Obsoletes rfc5721)
- 7162: IMAP Extensions: Quick Flag Changes Resynchronization (CONDSTORE) and Quick Mailbox Resynchronization (QRESYNC) (Obsoletes rfc4551, rfc5162) (Updates rfc2683)
- 7377: IMAP4 Multimailbox SEARCH Extension (Obsoletes rfc6237) (Updates rfc4466)
- 7628: A Set of Simple Authentication and Security Layer (SASL) Mechanisms for OAuth
- 7677: SCRAM-SHA-256 and SCRAM-SHA-256-PLUS Simple Authentication and Security Layer (SASL) Mechanisms (Updates rfc5802)
- 7888: IMAP4 Non-synchronizing Literals (Obsoletes rfc2088)
- 7889: The IMAP APPENDLIMIT Extension
- 8437: IMAP UNAUTHENTICATE Extension for Connection Reuse (Updates rfc3501)
- 8438: IMAP Extension for STATUS=SIZE
- 8440: IMAP4 Extension for Returning MYRIGHTS Information in Extended LIST
- 8457: IMAP "$Important" Keyword and "\Important" Special-Use Attribute
- 8474: IMAP Extension for Object Identifiers
- 8508: IMAP REPLACE Extension (Updates rfc3501)
- 8514: Internet Message Access Protocol (IMAP) - SAVEDATE Extension
- 8689: SMTP Require TLS Option
- 8970: IMAP4 Extension: Message Preview Generation
- 9051: Internet Message Access Protocol (IMAP) - Version 4rev2
- 9208: IMAP QUOTA Extension (Obsoletes rfc2087)
- 9394: IMAP PARTIAL Extension for Paged SEARCH and FETCH