From: email@address.com
Subject: this should be rich text
To: email@address.com
Mime-type: 1.0
Content-type: multipart/alternative; boundary="SHA1-HASH"

--SHA1-HASH
Content-type: text/plain; charset=utf-8
Content-disposition: inline

this is some html text.
--SHA1-HASH
Content-type: text/html; charset=utf-8
Content-disposition: inline

this is some <strong>html</strong> text.
--SHA1-HASH--
