Disable Dr. Web Notifications in Plesk
You can edit /etc/drweb/drweb_qmail.conf to eliminate receiving notification messages when Dr. Web has an issue:
[VirusNotifications]
SenderNotify = no
AdminNotify = no
RcptsNotify = no
Then just restart Dr. Web with:
/etc/init.d/drwebd restart
Plesk has a KB article about this issue as well.