I noticed that when we email purchase orders via SE, they come from "noreply@shippingeasy.com". This doesn't look good and based on what I've read about email marketing is pretty likely to end up in a spam folder.
Have you guys considered enabling SPF/DKIM so that you can send emails on my behalf? This insures that vendors get my PO as it is legit beind send on behalf of "allen@domain.com" for example.