I've found some interresting doc about mshtml feature, so I was able to fix some long time issue with the message editor in MyOE and add some useful feature.
- Upload attachment instead of sending them
- Add image miniature in mail, upload original images
- Spell Checking support
- MyOE now give an approximation of the message size in the status bar.
- When you it enter inside a quoted message, you'll be able to add your comment/answer without the quote bar. (in short: it works as expected).
- Zip attachment is back!