Resetting a password

I have restored a copy of a post office(GW 8) onto a stand alone pc. I have setup the GW 8 client to access the po directly. Of course, the mailbox prompts for a password, which I do not have. The owner of the post office does not know what it was. This is a restored copy from a few months ago, so no password available.

My question, how can I reset/break the password on this account?