RFC Requests For Comment

SMTP - Simple Mail Transfer Protocol

RFC 5321 Simple Mail Transfer Protocol
How email is sent over the wire
RFC 5322 Internet Message Format
The structure of email messages, especially headers

MIME - Multimedia Internet Email Extensions

RFC 2045 - Multipurpose Internet Mail Extensions (MIME) Part One
The basics of creating a MIME message, headers and encoding
RFC 2046 - Multipurpose Internet Mail Extensions (MIME) Part Two
Different media types - text, images, etc - and multipart messages, needed for rich text and attachments
RFC 2047 - MIME Part Three: Message Header Extensions for Non-ASCII Text
Internationalized text or glyphs in subject lines or friendly from


RFC 6376 - DomainKeys Identified Mail (DKIM) Signatures
DKIM, a way to allow a sender to prove they're responsible for a message
RFC 4408 - Sender Policy Framework (SPF) for Authorizing Use of Domains in E-Mail, Version 1
SPF, aka Sender Permitted From, aka Sender Policy Framework


RFC 5965 - An Extensible Format for Email Feedback Reports
Sending automated reports when a user hits the "this is spam" button
RFC 6430 - Email Feedback Report Type Value: not-spam

More to be added...