snooping port 25 packets

[Doug Yeager <doug@xxxxxxxxxxxxxxx>]

i would like to use netfilter to snoop SMTP packets on my firewall.
has anybody done this?  is it possible?
i was leaning in the direction of trying to use the QUEUE target for 
user space processing.....but i'm not sure if that is the way to go.
once i send the packet to the QUEUE target, how do i put it back on the 
wire?
what i really want is a copy of each packet to port 25 sent to a user 
space program.

thx,
doug