Is it possible to add domain restrictions to the email address?

Is it possible to add domain restrictions to the email address, to validate that the email domain is not one of the free domains (hotmail.com, gmail.com, yahoo.com etc). I know we can use the REGEX but we are limited to a fairly short string to list all of the free domains. A better way to achieve this would be to call an Apex class to check whether the email address is acceptable.