Ownership of a mailbox isn't something that is controlled by the actual owner of the mailbox but by the Exchange administrator via Full Access permissions.
You can find details on how to set that here; Manage permissions for recipients in Exchange Online
changing the owner of shared mailbox
Previous owner of shared mailbox resigned last year without changing the ownership to another employee.
Owing to this absence of the owner for this mailbox, access permission cannot be granted to new employees who really need urgent.
Any ideas how we can reset (or switch) the ownership to new person without having the original owner?
2 answers
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Robert Sparnaaij [MVP] 1,816 Reputation points MVP
2022-07-05T08:53:13.197+00:00 -
Faery Fu-MSFT 19,021 Reputation points Microsoft Vendor
2022-07-06T03:18:17.873+00:00 Hi @Ran Choi ,
Administrator can grant Send on Behalf permissions for a standard user mailbox via the https://portal.office.com/adminportal/home#/homepage,
In the admin center, go to the Teams & Groups > Shared mailboxes page.
Click on the shared mailbox and click edit to add members to this mailbox.
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