RFC 5337: Internationalized Delivery Status and Disposition Notifications
Extends DSN and MDN formats to support internationalized addresses.
Standards & Protocols
RFC 4155: The Application/Mbox Media Type
Registers the application/mbox MIME type for the traditional Unix mbox mailbox format.
RFC 5524: Extended URLFETCH for Binary and Converted Parts
Extends IMAP URLFETCH to support binary and format-converted part retrieval.
RFC 2045-2049: MIME (RFC 2045 through 2049): Attachments and HTML Emails
Overview article covering all five MIME RFCs as a suite: format, media types, header extensions, registration, and conformance.
RFC 6409: Message Submission for Mail
Defines port 587 as the mail submission port, separating client-to-server submission from MTA-to-MTA relay on port 25.
RFC 4409: Message Submission for Mail
Earlier version of the submission RFC. Obsoleted by RFC 6409.
RFC 3464: An Extensible Message Format for Delivery Status Notifications
Defines the machine-readable DSN format used in bounce messages and delivery receipts.
RFC 6522: The Multipart/Report Media Type
Defines the multipart/report MIME type used to structure delivery status notifications and other administrative messages.
RFC 5965: An Extensible Format for Email Feedback Reports
Defines the ARF (Abuse Reporting Format) used in Feedback Loop (FBL) complaint reports from mailbox providers.
RFC 2142: Mailbox Names for Common Services, Roles and Functions
Defines standard role mailboxes every domain should maintain: postmaster@, abuse@, hostmaster@, etc.
RFC 5598: Internet Mail Architecture
Conceptual overview of the entire internet mail system: MSA, MTA, MDA, MUA roles and their interactions.
RFC 6647: Email Greylisting: An Applicability Statement for SMTP
Formalises the greylisting technique where MTAs temporarily reject unknown senders to filter out botnet spam.
