RFC 2449: POP3 Extension Mechanism
Defines the CAPA command that lets POP3 clients discover server capabilities.
Standards & Protocols
RFC 1734: POP3 Authentication Command
Defines the AUTH command for POP3, enabling SASL-based authentication methods beyond USER/PASS.
RFC 2177: IMAP4 IDLE Command
Defines the IDLE extension that lets an IMAP client be notified of new mail in real time without polling.
RFC 4551: IMAP Extension for Conditional STORE Operation
Defines CONDSTORE, atomic flag updates with change detection to prevent race conditions in concurrent IMAP clients.
RFC 5256: IMAP Extensions: SORT and THREAD
Defines server-side message sorting and threading extensions for IMAP, reducing client-side processing.
RFC 6851: The IMAP MOVE Extension
Defines the MOVE command for atomically moving messages between IMAP folders without a COPY+EXPUNGE sequence.
RFC 7489: DMARC: Domain-based Message Authentication, Reporting, and Conformance
Ties SPF and DKIM together into a single policy record that instructs receivers how to handle failing messages.
RFC 8058: Signaling One-Click Functionality for List Email Headers
Defines the List-Unsubscribe-Post header enabling one-click unsubscribe, required by Google and Yahoo bulk sender rules since Feb 2024.
RFC 2369: The Use of URLs as Meta-Syntax for Core Mail List Commands
Defines List-Unsubscribe, List-Help, List-Post and other headers for automating mailing list management.
RFC 2919: List-Id: A Structured Field and Namespace for the Identification of Mailing Lists
Defines the List-Id header for uniquely identifying mailing lists, used by email clients to organise list mail.
RFC 6530: Overview and Framework for Internationalized Email
Framework RFC for EAI (Email Address Internationalization) supporting Unicode email addresses and headers.
RFC 6531: SMTP Extension for Internationalized Email
Defines the SMTPUTF8 SMTP extension that allows UTF-8 in MAIL FROM, RCPT TO, and headers.
