Go to Purchase Order and select the PO you want to send to your Supplier via email.
In the action bar at the bottom of your screen you select Email as Action. Check that the correct printout template as well as language has been selected, then click on Send.
A Pop-up appears with a preview of the email text that is going to be sent to your supplier with your PO as an attachment. If you are satisfied with it click on OK.
If you want to change the content of the email go to Settings - Purchase Order - Email Documents.