KAV Linux Files Server works using predefined jobs to scan the filesystem.
Clamav has a client-server model to submit files to scan to a daemon.
Clamav on SME is used for two different jobs:
1. daily/weekly scan of the filesystem
2. scan of email
KAV is ready for 1, but to scan email you should create and run a job on every mail. If possible at all, I think it would be hard to adapt sme and kav.
To scan email, the product is KLMS, but it supports postfix (I didn't check if it could be used with qmail).