Foundations

Message format, headers, MIME, identity, and the envelope.

3 topics in this category.

Internet Message Format (RFC 5322)
Required
Construct 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
Required
Emit mandatory RFC 5322 header fields (From, Date, Message-ID), structured recipient fields, and machine-readable metadata while preventing header duplication.
MIME Multipart Message Structure
Required
Structure rich email payloads using standardized MIME multipart trees (alternative, related, mixed), paired plain-text fallbacks, and collision-resistant boundary delimiters.