fetchmail/MS long shot

[Michael Masse]

I've read the archives and the wiki and have found plenty of information
on using fetchmail to pop messages from one email system and insert them
into another, but what I'm trying to do is a bit different, so I thought
I'd ask.     A certain ISP does a really bad job of spam detection and I
know it's possible to use fetchmail to download all of the mail from
that ISP and do MS / SA scanning on the mail, but is there a way to then
stick the ham email back on the ISP inbox so that the user doesn't
really have to do anything different in particular?   The problem I see
is how would fetchmail then know which messages have been scanned
already?   I'm not married to fetchmail if there is a better way to do
what I'm looking for BTW.

Mike