[courier-users] Courier as a filtering proxy

[Pierre O. <drz...@dr...>]

Hi!

I'd like to use courier as a filtering proxy for an Exchange server but
I'm not quite sure how to do it.

We currently have an Exchange server handling all of our mail. Getting rid
of it completely is not an option at the moment so I have to find a
different solution.
What I'd like to do is set up a machine running courier in front of the
Exchange server. The mail is received by courier, scanned for spam and
viruses and then forwarded to the Exchange server.

I know how to set up courier to act as a proxy, that is not the problem.
What I'm having problems with is the filtering. Since the mail isn't
delivered locally I can't pipe the stuff through a filter using maildrop
or similar.
What I've been looking at is the mail filtering that is performed on the
incoming mail (filterctl & co.). I assume these will examine the mail even
in this scenario. But from what I can gather these mail filters can only
accept or deny mail. I'd like to modify it. E.g. if the mail contains a
virus I'd like it to replace the mail with a warning and the original mail
as an attachment. And for spam it would add some extra headers (using
SpamAssassin).

If I write a filter that modifies the file courier gives it to parse, will
courier then use that modified file or the original copy?

Mvh/Rgds
Pierre Ossman