Notify User When Not Approved

It would be possible with a modification of the activation function. Unfortunately, that particular function is not currently pluggable and there are no filter/action hooks, so currently the only option would be to actually modify the function, which is not recommended.

The function, should you wish to modify it (and I’m not saying you should) is wpmem_a_activate_user found in /admin/users.php.

That’s a great idea though, so I’ll look into making some type of extension of that function available in a future update.

See http://wordpress.org/support/topic/you-are-not-authorized-to-see-this-part?replies=4#post-4322925