RFC 6531: SMTP Extension for Internationalized Email
Defines the SMTPUTF8 SMTP extension that allows UTF-8 in MAIL FROM, RCPT TO, and headers.
Email standards
RFC 6532: Internationalized Email Headers
Defines UTF-8 encoded headers for internationalized email messages.
RFC 2231: MIME Parameter Value and Encoded Word Extensions
Defines charset and language tagging for MIME parameter values, used in Content-Disposition filenames with non-ASCII characters.
Email RFC Directory: 68 Standards Explained
Reference catalog of 68 email protocol RFCs. Tiered by importance: essential standards every sender must know, complete reference catalog, and historical archive.
RFC 5322: Internet Message Format
Defines the structure of email messages: headers, body, encoding, and field syntax.
RFC 822: Standard for ARPA Internet Text Messages
The original email message format standard from 1982. Historical foundation of all subsequent format RFCs.
RFC 6152: SMTP Service Extension for 8-bit MIME Transport
Defines the 8BITMIME SMTP extension, allowing 8-bit message content without base64 encoding.
RFC 2046: MIME Part Two: Media Types
Defines the media type system (text, image, audio, video, application, multipart, message).
