Tumblr now supports Markdown via email
When sending Tumblr a mobile email post, you can now optionally include Markdown syntax to create rich text formatting.
Simply include
!min any part of an email’s subject or body to enable Markdown for that message. (The!mcode will be automatically removed from the final version.)
About frakking time.
The !m thing seems strange and likely to be forgotten, but better than nothing.