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Appendix B. Differences from Earlier Specifications

This appendix contains a list of changes that have been made in the Internet Message Format from earlier specifications, specifically [RFC0822], [RFC1123], and [RFC2822]. Items marked with an asterisk (*) below are items which appear in section 4 of this document and therefore can no longer be generated.

The following are the changes made from [RFC0822] and [RFC1123] to [RFC2822] that remain in this document:

  1. Period allowed in obsolete form of phrase.
  2. ABNF moved out of document, now in [RFC5234].
  3. Four or more digits allowed for year.
  4. Header field ordering (and lack thereof) made explicit.
  5. Encrypted header field removed.
  6. Specifically allow and give meaning to "-0000" time zone.
  7. Folding white space is not allowed between every token.
  8. Requirement for destinations removed.
  9. Forwarding and resending redefined.
  10. Extension header fields no longer specifically called out.
  11. ASCII 0 (null) removed.*
  12. Folding continuation lines cannot contain only white space.*
  13. Free insertion of comments not allowed in date.*
  14. Non-numeric time zones not allowed.*
  15. Two digit years not allowed.*
  16. Three digit years interpreted, but not allowed for generation.*
  17. Routes in addresses not allowed.*
  18. CFWS within local-parts and domains not allowed.*
  19. Empty members of address lists not allowed.*
  20. Folding white space between field name and colon not allowed.*
  21. Comments between field name and colon not allowed.
  22. Tightened syntax of in-reply-to and references.*
  23. CFWS within msg-id not allowed.*
  24. Tightened semantics of resent fields as informational only.
  25. Resent-Reply-To not allowed.*
  26. No multiple occurrences of fields (except resent and received).*
  27. Free CR and LF not allowed.*
  28. Line length limits specified.
  29. Bcc more clearly specified.

The following are changes from [RFC2822].

  1. Assorted typographical/grammatical errors fixed and clarifications made.
  2. Changed "standard" to "document" or "specification" throughout.
  3. Made distinction between "header field" and "header section".
  4. Removed NO-WS-CTL from ctext, qtext, dtext, and unstructured.*
  5. Moved discussion of specials to the "Atom" section. Moved text to "Overall message syntax" section.
  6. Simplified CFWS syntax.
  7. Fixed unstructured syntax.
  8. Changed date and time syntax to deal with white space in obsolete date syntax.
  9. Removed quoted-pair from domain literals and message identifiers.*
  10. Clarified that other specifications limit domain syntax.
  11. Simplified "Bcc:" and "Resent-Bcc:" syntax.
  12. Allowed optional-field to appear within trace information.
  13. Removed no-fold-quote from msg-id. Clarified syntax limitations.
  14. Generalized "Received:" syntax to fix bugs and move definition out of this document.
  15. Simplified obs-qp. Fixed and simplified obs-utext (which now only appears in the obsolete syntax). Removed obs-text and obs- char, adding obs-body.
  16. Fixed obsolete date syntax to allow for more (or less) comments and white space.
  17. Fixed all obsolete list syntax (obs-domain-list, obs-mbox-list, obs-addr-list, obs-phrase-list, and the newly added obs-group- list).
  18. Fixed obs-reply-to syntax.
  19. Fixed obs-bcc and obs-resent-bcc to allow empty lists.
  20. Removed obs-path.