FileMaker does not support any kind of formatting in emails in 10 or anything prior unfortunately. However you can achieve this using a plug-in, completely free, but 360Works called ScriptMaster
Comes with a great demo file and there are a few Email scripts to try out. A bit of a learning curve but a nice way to achieve what you want.
Thanks for the solution. FM10 can do extensive text formatting in scripts, however I'm trying to save money and use my existing FM3 version, and 360Works does not support that version. Thanks for the idea though!