You get emails which actually have a plain text part?
My e-mail reader is set for text and sometimes if I can't read a message inform the sender of that fact. They can take it from there.
In any case and just for the record, I just sent myself an e-mail with the subject "empty" and it came in at 579 bytes. I assume 5 of those were for the subject line.
I wouldn't fault the President on that though. He was just making a point.