Installation of Threat Prevention policy fails with Verification error.
When clicking on "Show Errors..." button, the following details are displayed:
<Name of Security Gateway> has MTA enabled, but it is not in the scope of any of the Threat Prevention policy rules.
Operation was unsuccessful.
Mail Transfer Agent (MTA) in enabled in the Security Gateway.
In such case, Threat Prevention policy requires that Security Gateway object is matched in the "Protected Scope" column of a rule.