Message filtering in a gateway setup

Hi!

I am currently using Axigen in a Gateway setup, where it is running in front of an Exchange server.
There are some accounts on the Axigen as well to facilitate Out of Office replies for former employees.

I would like to configure a message filter, which is activated on Axigen on special occasions, like an Auto-Responder that can be easily set for everyone instead of doing it manually for every individual user.

Is there a filter I can set up, that fulfills this, even if the mailboxes are not located on the Axigen servers ?

Thank you very much for your kind help.

Best Regards,
Manuel