The Zimbra Collaboration Suite installs the Clam Antivirus software as the anti-virus filter. By default, the anti-virus software is automatically enabled. You can modify these settings from the Global Settings>Anti-Virus tab.
The Zimbra MTA checks every two hours for any new anti-virus updates from ClamAV and updates to the software are automatically downloaded to the server. You can modify how often the MTA checks for updates. The frequency can be set between 1 and 24 hours.
The global settings for the anti-virus protection are configured with these options enabled:
Block encrypted archives, such as password protected zipped files.
Send notification to recipient to alert that a mail message to them had a virus and was not delivered.
Important: If you defined an anti-virus notification address during the installation of the Zimbra Collaboration Suite, create an anti-virus notification mailbox alias in your admin account, so that notification messages can be delivered to your mailbox.