emacs mail sends empty subject line

[ted]

I'm trying to send mail from emacs (21.3.1).  The trouble is that
recipients of my mail get empty subject lines.  They do see the subject
line, but as part of the body of my message!

So for example, if my emacs mail buffer looks like this...

To: bob@yahoo.com
Subject: hi
--text follows this line--

then my friend Bob gets mail with no subject line but with a message
body that starts with this exact header.

How can I get my intended subject line to actually appear on the
subject line?