Hi good people,
I have been struggling for a few days with a small problem with
Courier-MTA and would really value some advice to help me understand
what is happening.
We have a MS Exchange server and a recently installed Courier-MTA server
on FC4 behind a firewalled router. Needless to say we are migrating from
the former. The router forwards port 25 to Courier. Mail flows smoothly
except for one recipient out of some thousands that we regularly talk
to, that Courier cannot reach. When we mail to that person we get
maillog entries like:
Aug 8 08:36:40 hta21 courieresmtp:
id=0012ED09.42F5FD34.00000A25,from=<[EMAIL PROTECTED]>,addr=<[EMAIL PROTECTED]>:
451 Could not complete sender verify callout
followed by deferred. There are no other related entries here or in
syslog. The recipient can mail us and knows of no other mailer that has
problems with his address. The recipient's domain is directed to a
machine mailhost.planetdomain.com managed by a large ISP (iPrimus), who
incidentally use other mailhosts for their subscribed user base. I
thought initially that the remote machine could not callout the sender
here. However if we mail the same person through MSX it goes without a
hitch. My dim understanding of sender verify callout is that the remote
machine tries to start up a dummy mail delivery to the sender and aborts
after authentication occurs. As port 25 is forwarded to the Courier
server, we should see the same problem regardless of which mailer we use.
Is this maillog entry saying that Courier cannot get an authentication
for the user on the remote machine? The situation seems to be that the
issue is between Courier specifically and this particular remote machine.
What sort of tests can I use to track down the problem further? Is there
for example a way to change Courier's level of logging to see the
dialogue between the machines? I guess I could ultimately use a packet
logger. I'm not confident about getting the ISP to look at their logs,
but you never know.
We are using Courier pretty much out of the box, certainly as far as
esmtp is concerned. We are running ClamAV and Clamcour. I couldn't see
anything relevant in the docs or manpages or by google, but may not be
looking in the right places.
cheers, Ken
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