Autor: David Woodhouse Data: A: Boyle Owen CC: Exim list Assumpte: RE: FW: [Exim] BCC list at first MTA in chain - Any list, two
MTAsin series..
On Mon, 2003-03-10 at 09:23, Boyle Owen wrote:
> Excellent explanation - I had misunderstood the status of the To and Cc
> and so on. Of course; all that matters is the RCPT TO fields.. In that
> case, the delivery process is handled with maximum parsimony with each
> MTA making as few SMTP transactions as possible so that the mails fan
> out in a tree-pattern (I had feared a star pattern).
Well, it's not _quite_ perfect but it's close. Going back to the
example, if it transpired that 'anotherdomain' and 'yetanotherdomain'
are both clients of the same hosting provider, and so the mail for both
is in fact being sent to the _same_ remote host, Exim isn't going to
notice that, and hence is still going to make two separate connections
to the same machine.
This is because it'd just be too expensive to go through all the lookups
and _then_ compare for matches, and repeat the comparisons at each stage
when you fall back to a lower-priority MX host, etc.
And as Phil just said -- other MTAs won't necessarily be as efficient,
although I think most should.
