[Ryan07]

The ability to utilize HTML email is entirely based on the server, not the client (phone). For example, I had an EVO (now E4GT) and Windows 2003SBS at work. No HTML as it was not supported by that version of Exchange. We upgraded to 2011SBS recently and both phones could then have it.

I don't know anything about K9, but any app that delivers HTML email from a non supported server just converts it for your viewing pleasure.

Edit: spell check