We have vendors that require us to send purchase orders to multiple email addresses. I can't figure out how to make this happen on a per vendor basis when I create a new purchase order. Is it possible to associate multiple email addresses with a vendor such that each email address gets a copy of a purchase order?

Not natively, no. It will only send to a single email address. We use a paid bundle from The Vested Group that allows you to set certain contacts to receive certain transactional emails.

Thanks!