Hi, we did some work based on tgds's original https://github.com/tdgs/premailer-rails3 submitted fix for issue #51 (#51). We updated some classes where necessary, made sure the tests run, fixed a typo, and fixed perhaps one bug.
tgds + fixes + update
Don't add a duplicate of the text part
We found an issue with duplicate parts appearing in the output under certain circumstances, and updated our branch https://github.com/onehub/premailer-rails/branches/attachments-tgds.
Looks nice! I'll play with it when I find some time.