If there isn't an authoritative reference and there are differences in
semantics or syntax between the draft and RFC5321/5322 or future
revisions of these documents, it can lead to serious issues.
Standards Track documents are around years. The documents may be
edited by different authors as they get updated. Errors can happen;
the documents can diverge.
In my opinion, it is better to clarify that now or else we will end up
having discussions ten years from now to determine which
interpretation is correct or which standard to follow.
So. RFC 3501 (page 50-51), says that the localpart of a From: address is
matched case-insensitively when IMAP servers process SEARCH or UID
SEARCH commands. RFC 5321 says that SMTP servers process localparts
case-sensitively. Both rules go back essentially unchanged to very old
Do we need to discuss which is correct or which standard to follow? I
fail to see any conflict.