I find the HTML is generally unintentional on the part of the user.  They'd
shut it off if they could figure out how, because it irritates recipients
whose email client doesn't do HTML.

Don't blame the novice user - it's the stupid client software that defaults
to HTML for outgoing, or doesn't explain adequately.  Maybe the
installation routine asked, and it sounded good, so they checked it ...

What we need is a reflecter that would show us what our output message
looks like as-seen-by a couple dozen common email clients (anyone need a
project?).

Jim