Some root mail not coming through

[John Swartzentruber <jswartzen@xxxxxxxxxxxxx>]

I have an older server running RH9 that I use as a personal email server 
and webserver. I also host a few small mailman lists. That server has 
had some hardware problems, so I thought it would be a good idea to get 
another computer, which I did. I installed FC2 on it, then upgraded it 
to FC3. The plan is to switch back and forth during upgrades so that I 
always have something available. During this time, the original server 
is still my webserver and email server, but both computers are on my 
internal network behind a router which does port forwarding.

While both computers are up and running, I can get my daily log email 
messages from each computer using IMAP by accessing each server directly 
from my personal computer on my home network. On both computers, the 
/etc/aliases file has most addresses directed to root, then at the 
bottom directs root to "arthur" (on the old server) or "buster" (on the 
new server). These are also the names of the servers.

My master name server is handled by a server at my employer, which is 
remote. Both servers are running "named" in slave mode (I think). As you 
can tell, I'm mostly a newbie but know almost enough to be dangerous.

Anyway, that is all background. The problem is that yesterday I removed 
all port forwarding on my router, shut down arthur (the old server), and 
switched my port forwarding to send SMTP, HTTP, and DNS to buster (the 
new server). It looks like everything is working, but now, I no longer 
get my log email messages from buster (the new server).

Now this is the strange part: When I turn arthur back on, I receive my 
missing log messages on buster. Clearly there is some sort of dependency 
on arthur that is in buster, but I can't figure out what it is. I'm 
guessing it is DNS related, but don't know enough to find it.

Even when my log messages don't show up, I can send messages to 
"root@xxxxxxxxxxxx" and "buster@xxxxxxxxxxxx", and they show up just fine.

I'm stumped. Can anyone give me some pointers or guesses? I hope I've 
provided sufficient information.

Thanks