Here's how to report a LaTeX bug by Email:

Firstly
check that there really is a bug, by writing a short, self-contained document that shows the problem. You should make sure that the document doesn't use any third-party packages or document classes. If the bug turns out to be with third-party software, then please contact the developer, and not us!
Secondly
check to see if the bug has already been reported. You can do this by searching the LaTeX bugs database. If the bug has already been reported, then there may be a known solution to your problem.
Thirdly
run LaTeX on the file latexbug.tex, which will then prompt you for information about your problem, and will create a bug report message called latexbug.msg.
Lastly
mail latexbug.msg to us at latex-bugs@latex-project.org.
Then
wait with sending additional remarks about your submission until you have received the reply from the database that you message processed. The reply you get includes the number your bug was assigned in the subject line. Please, when sending further information about your problem, or when responding to questions posed by one of us, do not change the subject line (nor the cc: field for that matter). Keeping this simple rule makes sure that every bit of information which concerns your problem is kept within the same entry in the database.

If you do submit a report, thanks for taking the time!

Note: please use the mail address above only for bug reporting purposes; otherwise try the hints we provided for getting help.