Can I send HTML mails in Outlook Web Access?
There's a dropdown box when you create a new message through OWA - the two options are "HTML" and "plain text". If that box isn't there, there may be a problem with your Client Access server, or someone may have managed to remove it (though I'm not aware of any way to do this).
The dropdown box, where you can choose "html" or "plain text" is shown when you use firefox. You have to use Internet Explorer to see all the options.