Maps usernames to email addresses. Each line looks like:
This sends watch notifications to EMAIL_ADDRESS instead of to USERNAME at the repository machine. (All this really does is control the expansion of %s in the notify file.) If EMAIL_ADDRESS includes whitespace, make sure to surround it with quotes.
If user aliasing is being used in the passwd file, the username that will be matched is the CVS username (the one on the left), not the system username (the one on the right, if any).