Re: Open additional Office365 mailbox in Outlook 2010?

Hi Barrybemail,

You can assign the Full Access permission via PowerShell:

Here are the articles for your reference:

Connect Windows PowerShell to the Service: help.outlook.com/.../cc952755.aspx

Add-MailboxPermission: technet.microsoft.com/.../bb124097(v=exchg.150).aspx

Thanks,

Jerry Cen