A return address is important. Vendors need to be able to reply with confirmations and questions.
In store settings you can go to General - Shop Setup - and then choose your store to edit. We have multiple stores and mulitple buyers so one email address is not always the best. You can also add in your email in the from box of a PO if you are emailing directly to the vendor contact. Depending on the rep and their reliability I will email myself the PO and then forward it on them to make sure they received it. I would love to see where you can add to emails to the to field so I can send one to my rep and one to me for my tracking.