Ok....
You have a Partner Mail (looks like a wall-mounted PC...because that's what it really is).
Avaya's website has numerous documents for AT&T/Lucent/Avaya systems available for review. Here is the link for the Partner Mail:
http://support.avaya.com/edoc/docs/p...l/prm3piu1.pdf Page 48/388 lists where to find the various options in the Partner Mail's menu. 53/388 starts the discussion of how to create a mailbox.
Check out these pages and see if something helps.