Is there some special undocumented procedure (or workaround) that can make a
Word mailto: command generate an email with not just prefilled subject, but
also prefilled message body?

I know how to do it with HTML, but the resulting code doesn't work right
when edited into an HTML Word.doc's Mailto: hyperlink source code. It
generates emails with SOME body text, but that text is always randomly,
abruptly-truncated and has garbage characters around all carriage returns.

Thanks,
-Bob