Hello,
Have you tested by sending a test mail to this user?
I can reproduce the scenario that you mentioned. I can resolve this by following the workaround by sending a test mail to the user who has OOO enabled and then disabled. After sending the mail, the OOO status is removed in the Admin client.
The router only processes the out of office service when a message is received. The service will be turned off/disabled when the next message is received in the user’s mailfile. This is also true if the service is disabled automatically when the user’s designated out of office time has expired. If the user receives no emails after the out of office time period has expired or after user manually disables the out of office service then the service is disabled during routine router maintenance (4AM)
Thanks