HTML to Text Conversion?

I've read (somewhere) that some email programs contain code that can detect if a PC is configured to receive HTML or text emails.

In other words, you can send an email in HTML format, but if the email client detects that the receiver's PC can read only text, a text version will be displayed.

If this is possible, it would be very helpful, because I wouldn't need to worry about my email appearing as a garbled mess.

Does anyone here know of such a client, or code?

Thanks, as always...