Emails Blacklist allows setting email address patterns that are not allowed to sign-up to the service. This is useful in cases you would like to prevent certain email address or domain names from registration to the service.
Emails Blacklist blocks hotmail.com gmail.com and .edu domain names
How to add a new Blacklist rule
Click Add Rule to add a new rule
In the text-box enter a pattern. (For example blacklisteddomain.com)