It is built in.
I am using 1.2.2
To configure it go to:
Components > Community Builder > Configuration > Registration (tab)
The 5th item on the tab is "Ajax Email checker" and it has 3 settings.
Btw, I let the folks at Acymailing know you had already integrated with them. I had posted asking them to do it, then discovered the integration and posted back to the thread. They were thrilled.
I have also asked the folks at ChronoForms (
www.chronoengine.com/) if they would be willing to integrate by making a plug-in to their system - but I don't know if they have the manpower. I don't know if you are familiar with it, but ChronoForms is an extremely flexible, free forms building tool. Due to it's curl integration you can use it to front end many other forms. I successfully used chronoforms to add a user to 12All bulk mailing (non-joomla integrated) and if Registration Validator had directly integrated with ChronoForms I would have had a solution that could use your excellent code to validate submission to ANY mailing system. ChronoForm can natively create Joomla users, CB users and/or store all form data in a database. It makes a great leads collection system because you don't HAVE to create a joomla user to collect the data (sometimes this just clutters up the system with user ids that will never be used again) - so validating emails would be an awesome option.
Chronoforms has a plugin API.
Thanks for looking into this.
D.