RFC 3501 - Internet Message Access Protocol - Version 4rev1

Publication Date: March 2003
Status: Standards Track
Author: M. Crispin (University of Washington)
Obsoletes: RFC 2060

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Abstract

The Internet Message Access Protocol, Version 4rev1 (IMAP4rev1) allows a client to access and manipulate electronic mail messages on a server. IMAP4rev1 permits manipulation of mailboxes (remote message folders) in a way that is functionally equivalent to local folders. IMAP4rev1 also provides the capability for an offline client to resynchronize with the server.

IMAP4rev1 includes operations for creating, deleting, and renaming mailboxes, checking for new messages, permanently removing messages, setting and clearing flags, RFC 2822 and RFC 2045 parsing, searching, and selective fetching of message attributes, texts, and portions thereof. Messages in IMAP4rev1 are accessed by the use of numbers. These numbers are either message sequence numbers or unique identifiers.

IMAP4rev1 supports a single server. A mechanism for accessing configuration information to support multiple IMAP4rev1 servers is discussed in RFC 2244.

IMAP4rev1 does not specify a means of posting mail; this function is handled by a mail transfer protocol such as RFC 2821.

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Table of Contents

IMAP4rev1 Protocol Specification

• 1. How to Read This Document

  • 1.1. Organization of This Document
  • 1.2. Conventions Used in This Document
  • 1.3. Special Notes to Implementors

• 2. Protocol Overview

  • 2.1. Link Level
  • 2.2. Commands and Responses
  • 2.3. Message Attributes
  • 2.4. Message Texts

• 3. State and Flow Diagram

  • 3.1. Not Authenticated State
  • 3.2. Authenticated State
  • 3.3. Selected State
  • 3.4. Logout State

• 4. Data Formats

  • 4.1. Atom
  • 4.2. Number
  • 4.3. String
  • 4.4. Parenthesized List
  • 4.5. NIL

• 5. Operational Considerations

  • 5.1. Mailbox Naming
  • 5.2. Mailbox Size and Message Status Updates
  • 5.3. Response when no Command in Progress
  • 5.4. Autologout Timer
  • 5.5. Multiple Commands in Progress

• 6. Client Commands

  • 6.1. Client Commands - Any State
  • 6.2. Client Commands - Not Authenticated State
  • 6.3. Client Commands - Authenticated State
  • 6.4. Client Commands - Selected State
  • 6.5. Client Commands - Experimental/Expansion

• 7. Server Responses

  • 7.1. Server Responses - Status Responses
  • 7.2. Server Responses - Server and Mailbox Status
  • 7.3. Server Responses - Mailbox Size
  • 7.4. Server Responses - Message Status
  • 7.5. Server Responses - Command Continuation Request

• 8. Sample IMAP4rev1 Connection

• 9. Formal Syntax

• 10. Author's Note

• 11. Security Considerations

  • 11.1. STARTTLS Security Considerations
  • 11.2. Other Security Considerations

• 12. IANA Considerations

Appendices

• Appendix A. References
• Appendix B. Changes from RFC 2060
• Appendix C. Key Word Index

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Resources

• Official Text: RFC 3501 TXT
• Official Page: RFC 3501 DataTracker
• Errata: RFC Editor Errata

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Related RFCs

• RFC 2060: IMAP4rev1 predecessor (obsoleted by this RFC)
• RFC 2177: IMAP IDLE extension
• RFC 2244: IMAP4 Mailbox Name Attributes
• RFC 2821: Simple Mail Transfer Protocol (SMTP)
• RFC 2822: Internet Message Format
• RFC 1939: Post Office Protocol - Version 3 (POP3)