Use a custom content filter to allow Email Security to scan messages based on conditions you configure. Add or modify a custom content filter on the Main > Policy Management > Filters > Add (or Edit) Filter page. Email Security does not provide a default custom content filter.
Specify the conditions of your custom filter from a selection of criteria, including message attributes and operators, by clicking Add in the Filter Conditions box. In the Add Condition dialog box, select from among the following message attributes and operators to configure your custom filter (all message attributes except DKIM verification include a user-configurable Filtering criteria entry field):