It is the entity manager who activates, creates, deactivates, manages and deletes mailboxes.
Find more information in the FAQs:
EGT - How do you activate mailboxes in your organization?
EGT - What happens when you activate the mailboxes?
EGT – What are the consequences of activating and deactivating mailboxes?
EGT – How can you create a mailbox?
EGT – How can you delete a particular mailbox?