Bind outgoing SMTP traffic to specific IP address

[Phil Breskey <pbreskey@dotcomholdingsofbuffalo.com>]

Hi,

  Our mail server has multiple IP addresses assigned to it's network 
adapter.  When we send mail, qmail is using the first IP address 
assigned to the adapter, but I want to make it use one of the others. 
I've read that there was a patch by Markus Stumpf added to qmail 1.03 to 
do this (we're running netqmail 1.05), but I can't find anything about 
this patch on the LWQ site, and the link from the qmail.org site to the 
instructions on how to use it is broken.  I've also found suggestions 
via Google to do this with an iptables rule.  With all that said, I have 
a few questions:
Is the Markus Stumpf patch included in netqmail 1.05?

If so, can someone point me to where I can find the instructions on how 
to use it?
If the patch is included, would it be optimal to use the patch, or iptables?

Thanks!
Phil