This Extended service is designed for removal of duplicate items in the mailbox such as messages, folders, meetings, and appointments. It should not remove messages with the same subject, from the same sender and such, it only removes items with the same IDs which supposed to be unique.

Upon placing this request you will have to specify the mailbox in question.

Since this request is related to permanent deletion of mailbox items, it’s recommended to backup the mailbox before placing it.