Unity 5.0 in VM-only environment with UCM 6.1; Exchange cluster off-box - no Unity inbox.
This environment has been up for over a year, but suddenly there are many users with failed send receipts in their in-box when they check their messages. All of them are time-stamped late at night, and none of the users actually tried to send a message at any time. Unity is my weak-spot, so I'm not sure what to look for. Originally I thought that maybe the Exchange server was to blame, but if so I don't know how so. Thanks.