Enrolment

This is something we've recently done with this situation. When a users attempts to log in and is redirected to that Invalid Login page/message, they will see a "Forgotten your username or password?" link: there is a setting that allows the admin to decide what URL that link directs a user to. If you create some external page, you can then have it display something like "If you forgot your password, please contact so-and-so. However, Suspended users and Inactive users cannot log into Moodle -- to see if you're account has been deactivated, please contact so-and-so."