I've read several good things about FlexMail but I don't currently use it. It claims to have HTML support built in, but like so many good things in life, it isn't free.
http://www.webis.net/products_info.php?p_id=mail&
EDIT: now that I think about it... wouldn't HTML email on a device that doesn't have an AntiVirus program open you up to security risks?
REF:
http://www.zzee.com/email-security/