RFC 3464: An Extensible Message Format for Delivery Status Notifications
Defines the machine-readable DSN format used in bounce messages and delivery receipts.
Message formatting
RFC 2183: Communicating Presentation Information in Internet Messages
Defines the Content-Disposition header that controls whether attachments are shown inline or as file downloads.
RFC 5322: Internet Message Format
Defines the structure of email messages: headers, body, encoding, and field syntax.
RFC 2822: Internet Message Format
Previous email message format standard. Obsoleted by RFC 5322 in 2008.
RFC 822: Standard for ARPA Internet Text Messages
The original email message format standard from 1982. Historical foundation of all subsequent format RFCs.
