Command by mail: Way to disable command?

Dear RT-Users,

I’m using RT4.0.1 with RT-Extension-CommandByMail-0.10.
On the whole, the email interface works like a charm.
There’s one use case, however, that causes an error.
Here’s the scenario: an automated email (from an outside system) gets sent
to an RT queue, creating a ticket in that queue. The outside automated email
system pre-formats the email with “Priority: normal” in the body of the
email. Since RT-Extension-CommandByMail-0.10 expects “Priority:” to be a
number, it throws an error. The error comes in the form of an email message
sent to the requestor with a subject of “Extended Mailgate Error”, and a
body consisting of the original message sent to the RT queue.

“But,” you say, “Use the optional configuration option

The CommandByMailGroup option would solve the issue, but the automated email
system sends the email as a user in the command by mail group (The email’s
"From: " line has an email from a user in the command by mail group in it).
Altering the email sent by the automated system is outside of our control.
Removing this user from the group would remove the functionality of the
extension altogether, thus making the Commandbymailgroup configuration
directive ineffective in this case.

Since the “Priority” command isn’t used by our organization, is there a way
to disable that command?
Or, if that’s not the right question to ask, is there a better way to solve
this problem?