auto join group by domain at registration

As my title suggests I am interested in having new registered users, who's email address is from a specific domain, registered to a predefined group.  This functionality is available in the administration menu.  However, I am not able to get it to work.
My companies email struction is  I am not sure if the firstname.lastname is causing an issue or not.   I set up a new Gmail account and tried it and still no success.

I have tried the autosubscribe plug in, and every user is automatically assigned regardless of domain :(

any suggestions?