Very often, you hear people barking at someone because the poor fellow happened to send an HTML-mail to a mailing list. Now I personally do not understand this at all. Just about every email client out there, supports viewing HTML mails, and so do all the web based mail sites. And HTML mails are specially useful when you want to put certain text in bold, some text in italics, a couple of words in red or you need a bulleted list of items. They do add a few extra KB to every mail, but even a low-bandwidth guy like me has no problems with handling an extra 5-6 KB per email I receive.