Foundations
Message format, headers, MIME, identity, and the envelope.
3 topics in this category.
About this category
This section collects production-verified specifications, implementation standards, and operational guidelines for foundations. Each specification provides clear compliance levels (Required, Recommended, Optional, or Avoid) alongside concrete testing methods and platform considerations.
Topics
Internet Message Format (RFC 5322)
RequiredConstruct structurally valid email messages adhering to RFC 5322 grammar, strict CRLF line endings, 998-character line limits, and standard header folding rules.
Essential Email Header Fields
RequiredEmit mandatory RFC 5322 header fields (From, Date, Message-ID), structured recipient fields, and machine-readable metadata while preventing header duplication.
MIME Multipart Message Structure
RequiredStructure rich email payloads using standardized MIME multipart trees (alternative, related, mixed), paired plain-text fallbacks, and collision-resistant boundary delimiters.