Restricting @domain

I think this is more of a feature request than a support one. It might be a good candidate for an LT sub-module.

You could add a validation function to the form that checks the domain.

By adding a domain restriction it would allow this form of registration serve as a method of insuring only members of your organization with a valid organization email account could register and provide accountability for security issues so I would find this feature very desirable.

Try https://drupal.org/project/domain_registration