I have an ex-user whose mailbox we are holding on to for some kind of retention policy reasons. He is receiving email in his personal gmail account forwarded from this mailbox. I did a test where I sent his mailbox on our server a message and he replied back via his gmail confirming he got it. There is no forwarding set in the delivery options for the mailbox. I've logged onto the account via OWA and deleted all rules. There are no transport rules doing this.
I tried using the "Message Tracking" and "Tracking Log Explorer" tools but for some reason I can't really figure it out. It's not working. I'm not getting any results. I'm guessing I'm using it wrong.
As far as I can tell there is no reason why it should be getting forwarded. Any other ideas where this may be set?