IMAP Bibliography

This page collects key RFCs and related documents for the Internet Message Access Protocol (IMAP) and closely related email infrastructure. It is inspired by the original IMAP.org “IMAP Documents: RFCs and Drafts” page, which was last updated in 2006, and extends it with newer specifications and status notes.

For a complete, always-current view of registered IMAP extensions, see the 👉 IANA IMAP Capabilities Registry.

1. Base IMAP Specifications

Current base: IMAP4rev2

  • RFC 9051 – Internet Message Access Protocol (IMAP) – Version 4rev2
    https://www.rfc-editor.org/info/rfc9051
    The current IMAP base specification (IMAP4rev2). It obsoletes RFC 3501 (IMAP4rev1) and incorporates many extensions and clarifications developed since 2003.

Historical base: IMAP4rev1

  • RFC 3501 – Internet Message Access Protocol – Version 4rev1 (obsoleted by RFC 9051)
    https://www.rfc-editor.org/info/rfc3501
    The long-standing base IMAP specification from 2003. Still widely implemented and referenced; superseded by IMAP4rev2 but historically important.

Earlier IMAP specifications (e.g. RFC 2060, RFC 1730) are fully superseded by RFC 3501 and now RFC 9051.

2. IMAP-Related RFCs from the Original IMAP.org Page

This section reformats the original IMAP.org list and adds basic status notes where relevant.

2.1 IMAP protocol extensions and practices

2.2 Authentication and security

  • RFC 5321 – Simple Mail Transfer Protocol (obsoletes RFC 2821)
    https://www.rfc-editor.org/info/rfc5321
    Current SMTP standard for message transfer. The original IMAP.org page pointed to RFC 2821; that has since been superseded by RFC 5321.

  • RFC 1939 – Post Office Protocol – Version 3 (POP3)
    https://www.rfc-editor.org/rfc/rfc1939.html
    POP3 remains relevant as a contrasting mailbox access protocol to IMAP.

3. IMAP RFCs Published After 2006 (Selected)

Since the original page’s last update (April 2006), the IMAP ecosystem has gained many new RFCs. This is not a complete list, but highlights widely referenced documents.

3.1 Core capability and registry documents

3.2 Synchronization and mailbox resynchronization

3.3 Capability negotiation and list/sort extensions

3.4 Internationalization and UTF-8

IMAP4rev2 (RFC 9051) incorporates internationalization aspects that previously required separate extensions.

3.5 Security and TLS

  • RFC 8314 – Use of TLS for Email Submission and Access
    https://www.rfc-editor.org/rfc/rfc8314.html
    Modern guidance on using TLS for IMAP/POP/SMTP submission; effectively supersedes earlier TLS guidance in RFC 2595.

3.6 Quotas and metadata

3.7 Other notable IMAP extensions

There are many more IMAP extensions beyond those listed here (e.g. ANNOTATE, CONTEXT, ESEARCH, various Sieve RFCs, etc.). For implementors, the IANA IMAP Capability registry and implementation-specific RFC lists (e.g. from Dovecot, Cyrus, Crymap, Stalwart) are helpful curated sources.

4. How to Use This Bibliography

  • Protocol readers / implementors

    • Start with RFC 9051 (IMAP4rev2) as the base spec.
    • Consult RFC 4314 (ACL), 7162 (QRESYNC), 5161 (ENABLE), and 5530 (response codes) for commonly used extensions.
    • Refer to the IANA IMAP Capabilities registry when defining or consuming new capabilities.

  • Operations and architecture

    • Use RFC 2683 and RFC 2180 for implementation and multi-access guidance.
    • Use RFC 8314 and RFC 5321 for modern security and SMTP guidance.

This page will evolve as the IMAP ecosystem changes. If you spot omissions or mistakes, let us know via the contact channels on imap.org or easyDNS.