This may be way off-topic. If so, I apologize in advance.
I have been noticing some strange behavior with DNS lookups that seems to
affect Exim only.
From time to time, all outbound mail will suddenly stop working. Clients
(mainly Netscape) trying to send mail will time out.
In my mainlog, I get the following error for these messages:
lookuphost defer (-1): host lookup did not complete
I am running a caching-only nameserver on the mail host (it is listed first
in /etc/resolv.conf), and have 3 other nameservers outside the local LAN
available to me.
In the meantime, everything else is working just fine. Folks are browsing,
mail is being received, SSH sessions continue normally.
The mail server running Exim is behind a NAT device (Cisco 805) which is
doing port forwarding for inbound requests. If I reboot that device, the
mail delivery (namely lookups) works again.
I am utterly mystified by this behavior.
There doesn't appeart to be anything in my exim.conf file that would bear
any relation on this, with the possible exceptions of:
host_lookup = *
sender_verify
receiver_verify
My forehead is getting sore, and my desk is developing a groove from the
constant bashing of my head.
Thanks for any and all hints.
---
Craig Sprout
Network Administrator
Crown Parts and Machine, Inc.
http://www.crownpartsandmachine.com
