Error Message: Event ID 1722: An Unknown SMTP Command Occurred

If you have Internet Security and Acceleration (ISA) Server installed with Simple Mail Transport Protocol (SMTP) content filtering enabled, the following event may occur:

If the SMTP content application filter is installed, you must explicitly state which SMTP commands are permitted. Event 1722 occurs if you do not explicitly state the SMTP commands that are in use.

To resolve this issue, add the appropriate SMTP command in the application filter. Or, you can disable SMTP content filtering if it is not necessary.