Transparent SMTP proxies?

[Bill McGonigle]

Does anybody have a recommendation for a transparent SMTP proxy?    
I've found:

   DSpamPD <http://caspian.dotconf.net/menu/Software/DspamPD/>
   ASSP <http://assp.sourceforge.net/>
   smtpprox <http://bent.latency.net/smtpprox/>
   qpsmtpd <http://smtpd.develooper.com/>
   smtp-proxy <http://smtp-proxy.klolik.org/>

I'd like to put one on my open wireless access point so I won't allow  
Windows spam trojans to do their nasty on it and get my IP  
blacklisted.  I don't think I want spam filtering, just AV (via  
ClamAV), and perhaps some connection rate throttling.  I pretty much  
just want things to work normally for any kind of SMTP user, and I  
prefer postfix if all other things are equal.

Before I go try them all I figured I'd see if anybody here has done  
it already.

Thanks,
-Bill

-----
Bill McGonigle, Owner           Work: 603.448.4440
BFC Computing, LLC              Home: 603.448.1668
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