looking into spamassassin mail proxy solution

I am trying to find a mail proxy/spamassassin solution for 2 situations.  
Situation 1 is
  Mail Server --> Mail Proxy --> Internet

Situation 2 is
  Mail Client --> Mail Proxy --> Mail Server

Mail Proxy is on a seperate server.

I think MailScanner will work but after reading through part of the documentation still am not sure.  Pop3Proxy might work but there doesn't appear to have been much work on it, in some time.

I could of sworn that I saw a document on how to do this in the not to distant past, but now I can't seem to locate it.