Hi, the service looks neat.
As others found the verification is a bit clunky and delete email address doesn't work.
I'm working on an email app, which converts HTML/plain text to markdown. Not yet released :)
As far as see the plain/text is written markdown. I would suggest you modify content type to be
"Content-Type: text/plain; charset=utf-8; format=flowed; markup=markdown"
In this case, an email client will know it is markdown and can use it without conversion.
"Mail Mate" mac app support it, hopefully, my app for iOS soon.