i installed qmail-scanner and run the test_installation.sh using the qscand account.
the result is
QMAILQUEUE was not set, defaulting to /var/qmail/bin/qmail-scanner-queue.pl for this test...
Sending standard test message - no viruses...
qmail-inject: fatal: qq temporary problem (#4.3.0)
Bad error. qmail-inject died
the content of /var/log/maillog is
Feb 26 12:15:59 linux10 X-Qmail-Scanner-1.25: [linux10.perridot.my110944895949315159] owner of unpacked file "/var/spool/qmailscan/tmp/linux10.perridot.my110944895949315159/1109448959.15162-0.linux10.perridot.my" (uid=0) doesn't match UID of Qmail-Scanner (uid=502) - can't expect this to work. Fix whatever is creating files with uid=0
qmail-scanner error