[exim] trnsparent pop3/smtp proxy

Hi Dear
up now, for scanning incoming and outgoing messages, in company 's gateway, p3scan+proxsmtp+spamassassin were installed.
I think exim is more powerfull than p3scan or proxsmtp, if can acts as transparent proxy, can not it?

in first searching i can not find any related info.
let me know , can I combine exim with spamassassin for my purpose?
best
Pezhman