This week I had an Office 365 migration, with a very strage case:
I migrated all of the users to Office 365 with AADConnect, and when creating a new outlook profile, directly some additional mailboxes were added.
There were NO mailbox rights set yet !
I’ve checked the mailbox rights with powershell, en there were no active settings.
I’ve created a ticket @Microsoft and tested several things.
Solution 1:
Go to the attribute editor of the affected User, en select the attribute : msExchDelegateListLink
Delete all the available users, en delete them from the list => Click OK 2 times and sync again with AADCOnnect
Solution 2
Go to the server where AADConnect is installed, and start the “Synchronization Rules Editor” => Select “In from AD – User Exchange” => Edit
Select No
Go to Transformations => go to msExchDelegateListLink => Change the Flowtype to Expression => change the source to “NULL”=> click Save.
Solution 3
Completely reinstall The AADConnect, and deselect the attribute msExchDelegateListLink