One of our mailboxes is generating duplicate queue items in its queue. The other mailboxes/queues function without problems.

When I check the duplicate queue items in detail, I only see a difference in the Created/Modified by (delegate) fields:

The cause of the problem could be that someone gave the mailbox Dynamics access rights a little while ago. But that has been solved already. 
Besides that the configuration of the environment has not been changed (MS updates maybe)...

What I checked so far:

  • No workflows on queue items of queues
  • No routing rules
  • No mailbox sync errors
  • Configuration of the mailbox and the queue are the same for other queues in the same environment (not experiencing this problem)

Unfortunately this is a production queue, so I cannot recreate it.

It is a Dynamics online (Version 1710 ( ) with Exchange online environment.

Anyone has a suggestion?

Thanks a lot!