Many antispam programs work as mail proxies (just like avast) These proxies generally use the same ports but can be configued to work together. I use Spampal (an antispam mail proxy) in conjunction with avast!
I am not familiar with Mailmate but I expect that if they are like most antspam proxies they will have support and documentation for setting it up with antivirus programs at their site. If not you may get some ideas on how to do it by perhaps visiting the Spampal site (
www.spamplal.com) and review their documenation on setting Spampal up with various antivirus programs. The general concepts should (and do work) for most mail proxies when you want to "chain" them together.
If you want avast to filter all mail (including the spam) I think you need to chain your proxies this way:
Outlook ---> Mailmate ---> avast! --->pop3 server
Chained this way avast will have disinfected all the mail before Mailmate gets it.
Sean D