During our public beta (which will probably be through December) we are handling all outgoing and incoming mail for Postmatic-related email. Nothing goes through your web host. We are doing this because email delivery is notoriously difficult to troubleshoot. If we take most of the acronyms (ISP, DNS, SMTP etc) out of the way doing a large-scale test of our infrastructure becomes much easier. Right now if you visit our support site to tell us your post didn’t get delivered we know exactly who to blame. Us!