Deploying SA on a large mail site

[Gavin Cato <Ga...@corp.nexon.com.au>]

Hi,
 
I was wondering if anyone would mind giving me ideas on how to implement
this.
 
I need to deploy SA at a reasonably large mail site. We have a single
large server running FreeBSD that recieves the mail for
ourdomain.com.au. Users of that domain also pop off this server. I'll
call this server "Server A".
 
I don't want to run SA on that machine if possible as it's already a
pretty busy machine.
 
I have another grunty machine running SA on FreeBSD that I want to
integrate into the mix somehow but I can't quite grasp how to do this.
This box has SA configured with sendmail for global system use, and is
running well. I've already configured a few dozen domain names as having
it as their primary MX and then using /etc/mail/mailertable to forward
the "spam checked" email to their real mail servers. This server can be
called "Server B".
 
Theres 2 theoretical ways I can think of to integrate it.
 
1) 
 
Server B is primary MX for "ourdomain.com.au". When it recieves a
message, it makes a database call to "Server A". It then either scans
the message for spam/virus or just simply forwards it to "Server A"
unchecked.
 
As to actually how to configure this, that I'm not sure of. Does SA have
any code to check against a database/list of email addresses as to
whether it should scan them or not?
 
2)
 
Server A is primary MX. When it recieves a message it then compares it
against a local database/list, and if necessary it then forwards the
message to "Server B". Server B then scans it and then forwards it back.
I'm guessing this would annoy sendmail with a mail loop.
 
Any ideas? I'm not a guru with sendmail but I can generally get most
things done once I've got a rough lead.
 
cheers
 
Gav