Understand different email protocols for secure and efficient communication.
Email Protocols
RFC 5598: Internet Mail Architecture
Conceptual overview of the entire internet mail system: MSA, MTA, MDA, MUA roles and their interactions.
RFC 2392: Content-ID and Message-ID Uniform Resource Locators
Defines cid: and mid: URI schemes for referencing MIME parts within a message, used in HTML emails with embedded images.
RFC 1939: Post Office Protocol Version 3 (POP3)
Defines the POP3 protocol for downloading email from a server to a local client.
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 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 6530: Overview and Framework for Internationalized Email
Framework RFC for EAI (Email Address Internationalization) supporting Unicode email addresses and headers.
RFC 8314: Cleartext Considered Obsolete: Use of TLS for Email Submission and Access
Mandates TLS for SMTP submission (port 465/587), IMAP, and POP3. Declares cleartext email protocols obsolete.
RFC 2049: MIME Part Five: Conformance Criteria and Examples
Defines MIME conformance levels and provides worked examples for implementers.
RFC 2822: Internet Message Format
Previous email message format standard. Obsoleted by RFC 5322 in 2008.
