Give one user full control of another user’s mailbox in Office 365

To give your­self or anoth­er user full access to some­one else’s mail­box in Office 365 you have to use pow­er­shell. It can’t be done online.

Mailbox access

In this exam­ple we are going to give Pieter full access to the mail­box of Danielle use this com­mand:

Add-MailboxPermission  -User -AccessRights FullAccess

Inbox access

As an alter­na­tive you can also give per­mis­sions to an inbox only

Here’s the code:

Add-MailboxFolderPermission -Identity\Inbox -User -AccessRights Owner


For more detailed infor­ma­tion, please refer below arti­cle:

Give an Admin­is­tra­tor the Abil­i­ty to Open and View the Con­tents of a User’s Mail­box( )