When clicking 'Mailbox Assignment' and attempting to remove an 'Assigned Mailbox' the red 'X' button is missing.
The ability does exist and function if clicking 'Mailboxes', finding a mailbox and clicking Edit to view 'Users who can access Mailbox'; check the user to remove and click the 'Remove Access' button.
Perform an 'IISReset' on the server hosting IIS.
If the ability to remove the mailbox assignment is also missing from 'Mailboxes' confirm the account logged in has a Security Role assigned which includes the 'Edit Mailboxes' security action.
