$mail1_invitationsent $mail2_invitationsent $mail3_invitationsent ($college_name) $mail_contents $mail4_invitationsent $mail5_invitationsent
You may have to change your Content-type header to a charset other than utf-8. I believe that's 8-bit ASCII.
Btw, please use [ code ] tags. It keeps formatting, which makes code easier to read.