imp webmail, cyrus imap and virus filtering

[andreas moroder]

Hello,

we have a imp/postfix/cyrus system. The mail that goes out and comes in
from/to our system via smtp is checked by trendmicros virus wall.

The problem is mail that remains in our mailsystem and is accessed via
imap from imp. Viruswall has no way to check this mail.

Is it possible to write a sieve filter to start a virusscan on this mail
( by scanning the specific file in the users mail directory ? ) every
time a mail is created or read via imap ?

Thanks
Andreas