10:  Where should I report bugs and other problems with Emacs?

  The correct way to report Emacs bugs is by e-mail to
  bug-gnu-emacs@prep.ai.mit.edu.  Anything sent here also appears in the
  newsgroup gnu.emacs.bug, but please use e-mail instead of news to submit
  the bug report.  This ensures a reliable return address so you can be
  contacted for further details.

  Be sure to read the "Bugs" section of the Emacs manual before reporting a
  bug to bug-gnu-emacs!  The manual describes in detail how to submit a
  useful bug report.  (See question 3 if you don't know how to read the
  manual.)

  RMS says:

    Sending bug reports to help-gnu-emacs (which has the effect of posting
    on gnu.emacs.help) is undesirable because it takes the time of an
    unnecessarily large group of people, most of whom are just users and
    have no idea how to fix these problem.  bug-gnu-emacs reaches a much
    smaller group of people who are more likely to know what to do and have
    expressed a wish to receive more messages about Emacs than the others.

  However, RMS says there are circumstances when it is okay to post to
  gnu.emacs.help:

    If you have reported a bug and you don't hear about a possible fix,
    then after a suitable delay (such as a week) it is okay to post on
    gnu.emacs.help asking if anyone can help you.

  If you are unsure whether you have a bug, RMS describes how to tell:

    If Emacs crashes, that is a bug.  If Emacs gets compilation errors
    while building, that is a bug.  If Emacs crashes while building, that
    is a bug.  If Lisp code does not do what the documentation says it
    does, that is a bug.