On Tue, 4 Jul 2006, Adam Funk wrote:
> Out of curiosity, why does Exim's default behaviour (using a vanilla
> config file) accept a message without Date and Message-ID headers and
> relay it without adding them? Does adding "control = submission" have
> any other, possibly undesirable, effects?
Because it is confusing if it adds them, and (when relaying) contrary to
RFC 2821. (It used to; the change was made at release 4.30).
control=submission is intended for first submissions to the MTA from
MUAs. An MTA shouldn't be tampering with messages that come from other
MTAs, especially if it is relaying them. That is said somewhere in one
of the RFCs - ah yes, here's what 2821 says: "In general, a relay SMTP
SHOULD assume that the message content it has received is valid and,
assuming that the envelope permits doing so, relay it without inspecting
that content." Later, it says "As discussed in section 2.4.1, a relay
SMTP has no need to inspect or act upon the headers or body of the
message data and MUST NOT do so except to add its own "Received:" header
(section 4.4) and, optionally, to attempt to detect looping in the mail
system (see section 6.2)."
--
Philip Hazel University of Cambridge Computing Service
Get the Exim 4 book: http://www.uit.co.uk/exim-book
