If I use the online editor (2.0 latest drupal 5.8) and type a message.
Then click next to see preview and send test email.
If I then click previous to go look at the message to fix it up after the test mail it is gone (firefox 3)
I tried the FCK editor patch to see if it would help and same problem.
For now people can upload html but this would have been great to finally say they can do it this way.