[BlueOnyx:13503] EMail clogging up - DNS?

[Jim Matysek]

We've had this happen every now and then, particularly during heavy 
usage times on the server.

Running 5106R on an Aventurin{e} VPS. What happens is that email sent to 
our hosted domains gets stuck in /var/spool/mqueue and not delivered. We 
can get thousands of messages stuck there in the course of several 
hours. When I shell into the machine and try an nslookup usms.org (our 
main domain), I get a timeout saying ";; connection timed out; no 
servers could be reached". So it appears that is the reason why the mail 
isn't getting through - it can't find the domain that is hosted on this 
server.

I've tried restarting DNS through the gui or via the command line using 
named restart to no avail. I've tried restarting sendmail via the shell. 
Nothing I try seems to un-stick this except re-booting that VPS. 
HOWEVER, if I notice the problem late at night I can just let it go and 
one of the automated nightly server tasks will un-stick it. Does anyone 
have any ideas what it is that may be working overnight that I can try 
via the command line? Re-booting is too big a hammer to hit it with 
during the day when we have important activities going on that we don't 
want to interrupt.

-jim