in-reply-to

IN-REPLY-TO  -  replace the IN-REPLY-TO field

Usage:  IN-REPLY-TO [text]

When you send a REPLY to a message, a field called IN-REPLY-TO is created
  automatically, with this format:
      In-Reply-To:  Your message of #date> at 
  You can use the IN-REPLY-TO command to change the IN-REPLY-TO field to 
  any other text you prefer.  You can also use it to insert an IN-REPLY-
  TO field in a message that you are not writing with the REPLY command.
  The IN-REPLY-TO command followed by the return key removes the field.

Example:
    Send>display in-reply-to
     In-Reply-To:  Your message of Sat, 28 Apr 1990 at 11:02 AM EST
    Send>in-reply-to Your message about the lab meeting Monday
    Send>display in-reply-to
     In-Reply-To:  Your message about the lab meeting Monday

For further help, type "help" and one of these topics:
  display   edit   reply-to   header-field