To defend your system from viruses, do not open suspicious email attachments, enable antivirus protection on the server side, if this service is provided by your hosting company, and be sure to have a firewall and antivirus software installed on your personal computer. Also keep your operating system up-to-date and timely install security hot fixes and patches.
To switch on antivirus protection for a mailbox:
When an infected message comes, you will be notified by email. If Kaspersky Antivirus is used by your provider, then you might be able to configure it in Mail > email address > Antivirus tab.
To switch off antivirus protection for a mailbox: