| 1652 | SMTP Service Extension for 8bit-MIMEtransportJ. Klensin, N. Freed, M. Rose, E. Stefferud, D. Crocker · obsoleted by RFC 6152 | Draft Standard | July 1994 |
| 1870 | SMTP Service Extension for Message Size DeclarationJ. Klensin, N. Freed, K. Moore | Internet Standard | November 1995 |
| 2034 | SMTP Service Extension for Returning Enhanced Error CodesN. Freed | Proposed Standard | October 1996 |
| 2088 | IMAP4 non-synchronizing literalsJ. Myers · obsoleted by RFC 7888 | Proposed Standard | January 1997 |
| 2119 | Key words for use in RFCs to Indicate Requirement LevelsS. Bradner | Best Current Practice | March 1997 |
| 2177 | IMAP4 IDLE commandB. Leiba | Proposed Standard | June 1997 |
| 2342 | IMAP4 NamespaceM. Gahrns, C. Newman | Proposed Standard | May 1998 |
| 2920 | SMTP Service Extension for Command PipeliningN. Freed | Internet Standard | September 2000 |
| 3030 | SMTP Service Extensions for Transmission of Large and Binary MIME MessagesG. Vaudreuil | Proposed Standard | December 2000 |
| 3207 | SMTP Service Extension for Secure SMTP over Transport Layer SecurityP. Hoffman | Proposed Standard | February 2002 |
| 3461 | Simple Mail Transfer Protocol (SMTP) Service Extension for Delivery Status Notifications (DSNs)K. Moore | Draft Standard | January 2003 |
| 3501 | INTERNET MESSAGE ACCESS PROTOCOL - VERSION 4rev1M. Crispin · obsoleted by RFC 9051 | Proposed Standard | March 2003 |
| 3516 | IMAP4 Binary Content ExtensionL. Nerenberg | Proposed Standard | April 2003 |
| 3676 | The Text/Plain Format and DelSp ParametersR. Gellens | Proposed Standard | February 2004 |
| 3749 | Transport Layer Security Protocol Compression MethodsS. Hollenbeck | Proposed Standard | May 2004 |
| 4146 | Simple New Mail NotificationR. Gellens | Informational | August 2005 |
| 4315 | Internet Message Access Protocol (IMAP) - UIDPLUS extensionM. Crispin | Proposed Standard | December 2005 |
| 4409 | Message Submission for MailR. Gellens, J. Klensin · obsoleted by RFC 6409 | Draft Standard | April 2006 |
| 4467 | Internet Message Access Protocol (IMAP) - URLAUTH ExtensionM. Crispin | Proposed Standard | May 2006 |
| 4468 | Message Submission BURL ExtensionC. Newman | Proposed Standard | May 2006 |
| 4469 | Internet Message Access Protocol (IMAP) CATENATE ExtensionP. Resnick | Proposed Standard | April 2006 |
| 4549 | Synchronization Operations for Disconnected IMAP4 ClientsA. Melnikov, Ed. | Informational | June 2006 |
| 4550 | Internet Email to Support Diverse Service Environments (Lemonade) ProfileS. Maes, A. Melnikov · obsoleted by RFC 5550 | Proposed Standard | June 2006 |
| 4551 | IMAP Extension for Conditional STORE Operation or Quick Flag Changes ResynchronizationA. Melnikov, S. Hole · obsoleted by RFC 7162 | Proposed Standard | June 2006 |
| 4731 | IMAP4 Extension to SEARCH Command for Controlling What Kind of Information Is ReturnedA. Melnikov, D. Cridland | Proposed Standard | November 2006 |
| 4954 | SMTP Service Extension for AuthenticationR. Siemborski, Ed., A. Melnikov, Ed. | Proposed Standard | July 2007 |
| 4959 | IMAP Extension for Simple Authentication and Security Layer (SASL) Initial Client ResponseR. Siemborski, A. Gulbrandsen | Proposed Standard | September 2007 |
| 4978 | The IMAP COMPRESS ExtensionA. Gulbrandsen | Proposed Standard | August 2007 |
| 5051 | i;unicode-casemap - Simple Unicode Collation AlgorithmM. Crispin | Proposed Standard | October 2007 |
| 5068 | Email Submission Operations: Access and Accountability RequirementsC. Hutzler, D. Crocker, P. Resnick, E. Allman, T. Finch | Best Current Practice | November 2007 |
| 5092 | IMAP URL SchemeA. Melnikov, Ed., C. Newman | Proposed Standard | November 2007 |
| 5161 | The IMAP ENABLE ExtensionA. Gulbrandsen, Ed., A. Melnikov, Ed. | Proposed Standard | March 2008 |
| 5162 | IMAP4 Extensions for Quick Mailbox ResynchronizationA. Melnikov, D. Cridland, C. Wilson · obsoleted by RFC 7162 | Proposed Standard | March 2008 |
| 5226 | Guidelines for Writing an IANA Considerations Section in RFCsT. Narten, H. Alvestrand · obsoleted by RFC 8126 | Best Current Practice | May 2008 |
| 5228 | Sieve: An Email Filtering LanguageP. Guenther, Ed., T. Showalter, Ed. | Proposed Standard | January 2008 |
| 5229 | Sieve Email Filtering: Variables ExtensionK. Homme | Proposed Standard | January 2008 |
| 5230 | Sieve Email Filtering: Vacation ExtensionT. Showalter, N. Freed, Ed. | Proposed Standard | January 2008 |
| 5231 | Sieve Email Filtering: Relational ExtensionW. Segmuller, B. Leiba | Proposed Standard | January 2008 |
| 5232 | Sieve Email Filtering: Imap4flags ExtensionA. Melnikov | Proposed Standard | January 2008 |
| 5246 | The Transport Layer Security (TLS) Protocol Version 1.2T. Dierks, E. Rescorla · obsoleted by RFC 8446, RFC 9846 | Proposed Standard | August 2008 |
| 5255 | Internet Message Access Protocol InternationalizationC. Newman, A. Gulbrandsen, A. Melnikov | Proposed Standard | June 2008 |
| 5256 | Internet Message Access Protocol - SORT and THREAD ExtensionsM. Crispin, K. Murchison | Proposed Standard | June 2008 |
| 5259 | Internet Message Access Protocol - CONVERT ExtensionA. Melnikov, Ed., P. Coates, Ed. | Proposed Standard | July 2008 |
| 5267 | Contexts for IMAP4D. Cridland, C. King | Proposed Standard | July 2008 |
| 5321 | Simple Mail Transfer ProtocolJ. Klensin | Draft Standard | October 2008 |
| 5383 | Deployment Considerations for Lemonade-Compliant Mobile EmailR. Gellens | Best Current Practice | October 2008 |
| 5435 | Sieve Email Filtering: Extension for NotificationsA. Melnikov, Ed., B. Leiba, Ed., W. Segmuller, T. Martin | Proposed Standard | January 2009 |
| 5442 | LEMONADE Architecture - Supporting Open Mobile Alliance (OMA) Mobile Email (MEM) Using Internet MailE. Burger, G. Parsons | Informational | March 2009 |
| 5464 | The IMAP METADATA ExtensionC. Daboo | Proposed Standard | February 2009 |
| 5465 | The IMAP NOTIFY ExtensionA. Gulbrandsen, C. King, A. Melnikov | Proposed Standard | February 2009 |
| 5466 | IMAP4 Extension for Named Searches (Filters)A. Melnikov, C. King | Proposed Standard | February 2009 |
| 5551 | Lemonade Notifications ArchitectureR. Gellens, Ed. | Informational | August 2009 |
| 5598 | Internet Mail ArchitectureD. Crocker | Informational | July 2009 |