It has been reported that a lot of our clients are experiencing bouncing emails when receiving emails from customers with the error message “User wasn’t found at domain or the mailbox is unavailable”. Those using Office 365 or a Microsoft Office 365 Product are the one experiencing this problem. This is happening across the board and we are investigating the root cause of this. The problem seems that started yesterday around noon and is affecting only incoming emails to random users, which make us believe it has something to do with Microsoft Services.
If you are encountering this problem you can open a support ticket with us to investigate.
As soon as we have an answer or solution we will notify you again.
Nova Computer Support