Hi Jim,
Recently i have problem with MVS. MVS stop sending email into yahoo, gmail, bing when someone place order to dealer (dealer using public email). The strange thing, when i change the dealer email into private web mail(such as mail@@MyWebSiteScripts.com) the email to dealer going true. When i change back into yahoo or gmail, no email sending. I have make sure the site email function working with send email to customer that using gmail or yahoo mail. Do the problem with tep_mail in checkout_process?