Guys,
I've had a weird problem with Sendmail misbehaving in a way I don't really understand. I've worked round the problem but I'd like to understand what was going on.
The MX for one of our domains, blah.com, pointed at an internal Exchange server. Mail relayed to a Sendmail MailScanner which then delivered to Exchange for this domain. The domain expired leading to all its mail queueing in Sendmail. So far so sensible.
While waiting for the domain to be renewed I setup a mailertable entry to bypass DNS and route mail directly to the Exchange server...
blah.com smtp:[192.168.10.10]
I rebuilt mailertable then tried flushing the queue with...
sendmail -q -v -qRblah
... which resulted in a bunch of "Transient parse error -- message queued for future delivery" errors due to DNS resolution failure.
I thought mailertable entries bypassed DNS? Does Sendmail cache the state of the destination for queued messages somehow? In the qf${msgid} files in the spool?
I tried restarting MailScanner (and hence both Sendmail processes), same problem. I read ( http://www.sendmail.org/~ca/email/doc8.12/op-sh-3.html ) that Sendmail can, when configured with HostStatusDirectory enabled, retain information on the status of hosts on disk but "sendmail -bh" returned nothing and "sendmail -bH", just in case, didn't help either.
So, was mailertable being bypassed because these messages had already been attempted to be delivered before the mailertable changes? Anyone know what was going on here? I worked around it by just setting up a quick zone for blah.com with an MX in it but I'd like to understand WTF was going on with mailertable for future reference.
Will.