Mail transport protection

SMTP server-level filtering is secured by a specialized plugin. In Microsoft Exchange Server 2003, the plugin in question (Event Sink) is registered on the SMTP server as a part of Internet Information Services (IIS). In Microsoft Exchange Server 2007, 2010, 2013, 2016 and 2019, the plugin is registered as a transport agent on the Edge or the Hub roles of the Microsoft Exchange Server.

SMTP server-level filtering by a transport agent provides protection in the form of antivirus, antispam and user-defined rules. As opposed to VSAPI filtering, SMTP server-level filtering is performed before the scanned email arrives in the Microsoft Exchange Server mailbox.