No HTML Mail, Please set your mailer to send only plain text messages to the list.
Try not to use MIME: a lot of people use mailers which do not get on very well with MIME.
in plain ascii text.
Post HTML at your own risk. Keep in mind that not everyone uses mail or news readers that can easily display HTML messages. Consequently, you will reach a larger audience if you post in plain-text. Many people simply ignore HTML messages, because it takes a nontrivial amount of effort to read them.
Please don't send HTML email. Send your email as plain text only.