mailscanner behind a smtpd frontend

[Philipp Snizek]

Hi


I have here an architecture I'm not too happy with. 
It looks like this:

inet -- smtpd -- antispam gw (mailscanner) -- LAN

The problem I see here is that the antispam gw gets mails with headers
from the smtpd. Thus, if the smtpd forwards spam the antispam gw learns
that (SA autolearn enabled). 
I'd prefer to have the antispam gw as a mail frontend. 
However, from firewalling point of view my client wants to make sure 
that only smtp transactions reach the antispam gw. 

I have following ideas how to deal with this problem:
a) have mailscanner remove the smtpd's received:from header line
b) tell SA to ignore the smtpd's received:from header line
c) use a transparent smtpd service

However, I wonder what of this is possible and if there are other
(better) ideas.

Thanks a lot

Philipp