the = characters in your message are a special coding line formatting which is not handled well by the lute mail robot. You will notice that Rob's part of the message has far fewer of these = signs. That is because he uses the return key to make each line shorter than 80 characters. If you use the return key at the end of each line, like one would on a typewriter, you will avoid this problem.
Now for the technical part..
You are sending mail as text/html and quoted-printable. The = sign is actually part of the quoted printable specification, and the lute mail robot does not handle it. If you were to set your "Content-Transfer-Encoding" to 7bit or plain or maybe ascii it might work better. I really can't tell you exactly how to do this because every mailer is a little different and I have no idea what mailer you use, and probably have never seen it either!)
the = sign is used to indicate that a long line (with no carriage return) is being broken into 80 character lengths to go through the mail, as some mail systems actually chop off the end of every line after 80 characters.
If all the mail browsers in the world used exactly the same format it would be much easier for me to write a robot to handle them all, but it isn't that way.