We have a Mitel 5000 where the customer recorded over the default system greeting, so whenever callers access someone's mailbox that is set for the standard system greeting, instead of primary or alternate, they hear the customer recording, then the system greeting immediately after.
I fixed a similar issue a few years ago, and I have poured through the system, including checking audiotext recordings, but I can't recall where to go to rerecord the mailbox system greeting.
Thanks, Jim