Your new group will initially be called ‘New Group (Custom) so right-click it select ‘Rename' and call it something else like ‘Attach File As' or whatever you fancy.Right-click ‘New Mail Message' and select ‘Add New Group'.On the right-hand side under ‘Customise this Ribbon' > Main Tabs select ‘New Mail Message'.
Update You can also use the Attach File > ‘ Insert as Text‘ via the Quick Access Toolbar (make sure it's ticked)when you create a new email, in which case you can jump to number 8 on this page.
