HTML E-mail: Must you send an alternate plain text view as well?

Question

When sending HTML e-mail, I understand that it's a best practice to send a plain text version as well.

But my question is: Must you send a plain text version as well?

What are the repercussions?

Answer 1

At least as far as Outlook 2007 is concerned, there are no reprecussions. We have an internal app that sends out emails in HTML format only and Outlook doesn't complain and renders the HTML content.

Sending an email with a plain-text version is simply common courtesy to support email clients that either don't support HTML format, or have their client set to render plain-text only. It's actually more prevalent than you may think so if you can either ask the user their preference or send both.