Drupal-User-Registration-Validation

This module validates information submitted on the user registration form. There are some hard-coded checks:

• disallow spaces in usernames
• disallow non-word characters and spaces in usernames
• disallow non-word characters in firstnames
• disallow non-word characters in lastnames
• apply a blacklist: disallow specific email domains (admin specifies)
• apply a whitelist: allow registration only from specific email domains (admin specifies)

To configure how the validation is done, there is an Administrative configuration panel under Admin > Config > People > User Registration Validation

It looks like this:

Modifying the checks

If you'd like to modify the checks, you can look in functions.inc for the dpchiesa_validate_userreg_available_checks function. Add or remove checks there, following the pattern. You should be able to figure it out.