Some time ago, I wrote some quick-and-dirty greasemonkey javascripts to parse plain text bodies of mail messages and mark up things such as quotes, so you could collapse/expand them, colour quotes differently depending on depth, etc. As a result of that experience and countless flamewars about top vs. bottom posting, I've often thought that a markup language specifically designed for email was a good idea. top/bottom posting could be a presentation decision of the client; you could GPG-verify quoted mail; conventions like 'Re:' could be internationalized, again on the client side, etc.

This morning I discovered Mail Markup Language which is exactly that. Unfortunately, it appears to have some outright bizarre features. The RFC draft describing it is enormous, including a full XSLT description of the markup language (and not in an appendix either); a legal preface claiming that the entire thing was patent pending (and using a subset of MML would be considered patent infringement); it claimes to obsolete 1939, 3501, 5322, which are POP3, IMAP4r1, and Internet Message Format respectively.

You shouldn't judge a book by it's cover, but the fact their website displays awfully for me (epiphany 2.22.x) did prepare me somewhat for the zaniness that followed.