We have resolved this in our enviroment for the moment. We had to create an in house application to reset the mailbox permissions on all the affected users on all of our exchange users. Investigations with Symantec showed the even if you are not vaul...
After spending a couple of weeks back and forth with support they are assuming it is caused by having multiple self permissions on mailboxs that were moved by our migration tools. Which is nearly impossible to verify, without resetting mailbox permis...