binding qmail to a specific ip address

[Leni Mayo]

I'm qmail running on a box with 2 network interface cards and want
to bind qmail to a specific IP address in order to simplify
firewall rules.  

I'm thinking along the lines of the apache "BindAddress" keyword,
so qmail would only use a specific ip address when listening and
as a source address for outbound connections.

If anyone has a hack for qmail 1.03 along these lines, I'd love to
see a copy of the source.

Leni.