RFC 1847: Security Multiparts for MIME: Multipart/Signed and Multipart/Encrypted
Defines MIME framework for signed and encrypted message parts, foundation for S/MIME and PGP/MIME.
RFCs
RFC 5751: Secure/Multipurpose Internet Mail Extensions (S/MIME) Version 3.2
Defines S/MIME 3.2 for signing and encrypting email using X.509 certificates.
RFC 1939: Post Office Protocol Version 3 (POP3)
Defines the POP3 protocol for downloading email from a server to a local client.
RFC 2449: POP3 Extension Mechanism
Defines the CAPA command that lets POP3 clients discover server capabilities.
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.
