<snip>
>   I may be misunderstanding what you mean by fixing the routing, but when
> postfix checks to 'reject_unknown_client'
<snip>

I think I was unclear on that point.  I mean the actual kernel level
network routing--essentially, when my servers attempt to send a data
packet they can do so via two pipes if you will, one for each of my public
IP addresses.  Before QuickBuild went down earlier all traffic was sent
out the .180 pipe.  Now, due to the network card change, all traffic is
being sent through the .181 pipe, which does not correspond to any of my
DNS entries and is apparently tripping up certain spam filters.

Changing all the DNS entries would be a somewhat irritating undertaking,
so I prefer to take this opportunity to better control the external IP
routing. :)

Tim