135: How do I change the included text prefix in mail/news followups?

  If you read mail with Rmail or news with Gnus, set the variable
  mail-yank-prefix.  For VM, set vm-included-text-prefix.  For mh-e, set
  mh-ins-buf-prefix.

  For fancier control of citations, use SuperCite.  See question 103.

  To prevent Emacs from including various headers of the replied-to
  message, set the value of mail-yank-ignored-headers to an appropriate
  regexp.