Please add permission to enable/disable "Show my email address" option

Hello,

I run a forum with Drupal 6, and the users make heavy use of private messages. Most of them prefer to keep their email addresses private, and I would also prefer to protect them from some of the dangers of leaking their email address to strangers. To prevent users from accidentally enabling the "Show my email address" option in the user profile, I would prefer a permission to "Enable users to send PM with their own email address" so I can disable it on a role basis.

I'm tagging this as a "major" "bug report" and not a "feature request" because at least in certain environments it is a very dangerous idea to send a private message with the user's email address in the header, so it's almost a security issue in my mind.

Thanks a lot for this powerful module.