Mail server software does not wrap lines in the body of the message.
The linewrap was done by the email client software you used to send
the message. Check your email software settings. Some email programs
allow you to explicitly specify the maximum line length for outbound
plain text messages; some do not. If you are using an email program
which does not allow you to explicitly specify the maximum line
length, you may want to set the width of the message composition
window to 75-80, then disable word wrap in the message composition
window. This will not prevent you from composing lines greater than
the window width, but it should make it obvious that you have done so.

(I read the list in digest mode, so I do not have access to the full
headers on your messages and cannot determine what email software you
are using.)

--
Paul Russell
Senior System Administrator
University of Notre Dame