Connect via powershel with the account that had given read access
Now let’s remove the permission to send on behalf of
Set-Mailbox –Identity firstname.lastname@example.org –GrantSendOnBehalfto $null
Now add the email account in Microsoft Outlook:
File | Account Settings | Double click on account | More Settings | Advanced | Mailbox | Add | Enter the name of the Mailbox. OK an all screens.