This quick, easy to follow guide will help you to grant full-access permissions to an O365 mailbox in minutes.

To get started open a remote session using this PowerShell:

Set-ExecutionPolicy RemoteSigned
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri -Credential $o365cred -Authentication Basic -AllowRedirection
Import-PSSession $session

In our first example, we’ll delegate full access  to a single mailbox. In this case, so that Jim has full access to Billy’s mailbox:

Add-MailboxPermission -identity [email protected] -user [email protected] -AccessRights FullAccess

In this example, we’ll give Jim full access to all mailboxes in the organization:

Get-Mailbox | Add-mailboxpermission -user [email protected] -AccessRights FullAccess

And that’s it, you’re done!