OT: difficulty with moving server

[Steve Campbell]

I'm trying to move one of our servers behind one firewall to another. I 
can't figure out what might be cached that prevents a smooth move. The 
mailserver is running a caching dns server, but the public IP for the 
mailserver is being moved to the new firewall, so I don't think it's DNS 
causing the problem.

It appears that when I have the machine moved, after stopping MS (along 
with sendmail), the firewall accepts a telnet on port 25 to another 
domain, but either the firewall or sendmail doesn't receive or accept 
the returning packet. I get nothing in my firewall logs for denials. Any 
arp tables are flushed that are in front of the mailserver and firewall. 
I do believe I discovered that sendmail retains routing information to 
it's default gateway. A check on the firewalls indicate the proper 
public IPs have been removed or installed. Mail travels into the server 
from the public lan and is sent and received behind the firewall. It 
just won't leave through the firewall to the public network.

Does anyone know of anything I might be overlooking from the 
mailserver's point of view that might be cached and hanging around? A 
reboot didn't solve anything for me, and I have similar mailservers 
behind the new firewall with the same set of firewall rules.

Thanks for any ideas and sorry for the OT.

Steve Campbell