Office 365: Grant a User Full Mailbox Access to all Mailboxes

KB ID 0001466


Obviously there are some security concerns about having a user with full mailbox access to all mailboxes! But that aside, I was using a third party Migration tool last week, and it needed to connect to every mailbox with full access rights to perform the migration.

So this is how I did it;


Firstly you need to connect to your Office 365 tenant with PowerShell;

Connect to Office 365 Exchange PowerShell

Connect PowerShell to Office 365

Now I could grant access to one user, but I’m going to create a ‘Group’, Exclude that group from the Global Address List, Put my user in that group. Then Finally grant the ‘group’ rights to all the mailboxes.

New-DistributionGroup -Name “365-Migration-Admins” -Type "Security"

Set-DistributionGroup "365-Migration-Admins" -HiddenFromAddressListsEnabled $True

Add-DistributionGroupMember -Identity "365-Migration-Admins" -Member ""

Get-Mailbox -ResultSize unlimited -Filter {(RecipientTypeDetails -eq 'UserMailbox')} | Add-MailboxPermission -User -AccessRights FullAccess -InheritanceType all

O365 Grant Full Mailbox Access to a User

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Author: PeteLong

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