Sending a rich text email from GMail to a Creator form results in plain text data being transferred. However, if you send the email from a Creator form using the rich text editor field to another Creator form, the rich text data is transferred!
I have identified that this discrepancy is due to how Creator sends an email. In most "normal" emails, there are two MIME blocks, one for plain text and one for rich text. For example, the parts will be separated and designed by this:
Content-Type: text/plain; charset=ISO-8859-1
Content-Type: text/html; charset=ISO-8859-1
The email from Creator (using the RTE field for the body) does not have a multipart MIME component. It's simply:
Content-Type: text/html;charset="UTF-8"
Since the email from Creator does not have the text/plain boundary, the rich text is transferred as expected.
The Creator teams needs to add some more logic to the email parser that accepts data emailed into forms. There will be cases where users want plain text added or rich-text added. Some emails may only come by plain text (like listserv), and some only using rich text (like the ones from Creator). But the developer needs to have some control over which one to use, if both a present in the raw email.