From: Reggie Sniff (rsniffamllc.com)
Date: Tue Jan 02 2007 - 13:38:18 CST

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I am hoping someone might help with this problem.

We are getting a "Host not found" error on one particular domain, but all
other mail is delivered fine.
I can get it do deliver if I *force* a different DNS server (instead of my
local server), but it only works if I actually edit the resolv.conf file.

For example, I can get around the problem manually by doing the following:
1) Edit the /etc/resolv.conf and remove the local nameserver from the first
line
     Remove the first line (nameserver 0.0.0.0)
2) Force sendmail to retry the queue (# sendmail -q)

Once I do this, it works, because it just uses another (working) DNS server
for the lookup.

dig results:
When I try:
# dig localhost mx hostname, the query files
   It seems my local server is unable to resolve the host and/or get a MX
records.
If I run:
# dig mx hostname, it works because fine
  This works because dig will eventually use a different DNS server from the
list in resolv.conf file

What I cannot figure is why Postfix does not work just like dig in that it
won't seem to use any of the other servers in the /etc/resolv.conf file to
resolve a host that my local server cannot seem to resolve.
It just fails with "Host not found" as long as my localhost is the first
line in the /etc/resolv.conf

What I am wondering is not how to fix my DNS problem, but rather why Postfix
doesn't get beyond the "Host not found" by trying another host in the
/etc/resolv/conf file....

FYI: I've confirmed that my mail server (with local DNS) cannot contact the
remote DNS because the command (# telnet remotedns 53) just times out

The server in question RH4 and is running Bind 9.2.
We are not running chrooted

Regards,

Reggie

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