Dr Web is an anti-virus email filter in the Plesk control panel. It can send daily emails by default, letting you know virus definitions have been updated and similar. You can disable these emails as follows:
1. Log on to your VM via SSH\command line
2. Edit the /etc/drweb/drweb32.ini file
3. Change the "CronSummary = yes" line to "CronSummary = no"
4. Restart dr.web by running the command: /etc/init.d/drwebd restart
You can see more in the Plesk knowledgebase: