Routing question?

[Kurt Buff]

All,

I have a FreeBSD 5.3 box running 
postfix/amavisd-new/spamassassin/clamav. Currently, we have two 
entrances to our network, one is the Watchguard FBIII for our T1, the 
other is a PC running Win2k and Winproxy, serving our DSL line. The PC 
is starting to flake out, and I'd like to replace it with a Wachguard 
SOHO that we have laying around.

The default gateway for the FreeBSD box is pointed at the WG FBIII, as 
that's the way most of our email comes through.

What the PC with Winproxy does is accept inbound email connections to 
our secondary MX, and presents them to the FreeBSD box. I'm assuming 
that the Winproxy program was doing something funky to make all of this 
happen, but I'm really set on replacing it. This has been working for a 
year or two, but lately the Winproxy program on the PC is falling over 
several times a day. It's not a hardware error - all other programs on 
the machine work just fine, but Winproxy is dieing.

When I hook up the SOHO, I can't get emails through the DSL line.

Does anyone out there know what I can do to set up the FreeBSD box so 
that email coming through on the DSL line can be handled?

One other detail that might affect the answers given - there are two IP 
addresses on the NIC in the FreeBSD box. One of those addresses handles 
the inbound emails (applying all of the savvy of 
amavis/spamassassin/clamav) and the other handles outbound mail, and no 
mail scanning happens to mail through that IP address.

Thoughts? Sneers?

Kurt