Grant a user or group full access to all exchange mailboxes

When preparing to migrate mailboxes to exchange online the account used for the migration will need full access to all mailboxes. It is advised to create a an account just for this purpose, I tend to create a domain account with the username “365-<RANDOM>”.

Replacing <RANDOM> with a random string of characters.

The below command will give the user full access to all mailboxes:

get-mailbox | Add-MailboxPermission -User '<DOMAIN\USER>' -AccessRights 'FullAccess'

Replace <DOMAIN> with the local domain name and <USER> with the required username or group.


Upon successful completion your <USER> will have full access to all mailboxes in your organisation .