Hi, I'm building something just like this called bip.io, throw away email addresses and identity protection are a 'feature' of a wider messaging API (its a glue platform, similar to ifttt or zapier or engineio). We're approaching a stable beta. If you'd like to try out the service, follow us on twitter @bipioapp and we will notify when the gates are open. Realistically about 4-6 weeks away, just putting it out there if you're looking for options...
(oh, and you can use whatever domain you can manage MX records for - its preferable in fact)
(oh, and you can use whatever domain you can manage MX records for - its preferable in fact)