En los logs aparecen errores como este:
Jan 20 15:42:42 securemail4 amavis3738: (03738-01) (!)WARN: all primary virus scanners failed, considering backups
Jan 20 15:42:44 securemail4 amavis3740: (03740-01) (!)run_av (ClamAV-clamd) FAILED – unexpected , output=“/var/lib/amavis/tmp/amavis-20160120T154244-03740-2uK8T_hT/parts: lstat() failed: Permission denied. ERROR\n”
Jan 20 15:42:44 securemail4 amavis3740: (03740-01) (!)ClamAV-clamd av-scanner FAILED: CODE unexpected , output=“/var/lib/amavis/tmp/amavis-20160120T154244-03740-2uK8T_hT/parts: lstat() failed: Permission denied. ERROR\n” at (eval 100)
Probar esta solución
A working solution is to change
AllowSupplementaryGroups false → true
in /etc/clamav/clamd.conf
restart clamav-daemon