HTML is also on by default in Netscape.  And sometimes,
even though I've turned it off in preferences, replying to an
HTML message forces me to use HTML.  (Unless I want to
do special tricks to defeat it.)

Back to the subject, my vote is to block HTML, PDF, and
all attachments.

I also vote to fix the thing that at least twice a year gratuitously
turns back ON the "send acknowledgement" option.

--
Wes Groleau
http://freepages.rootsweb.com/~wgroleau