Support to add a small checkpoint for checking if the email ids of invitee is not fake

Hi Folks,

Basically if user sends a invitation giving a fake id then it gets stored in the table. After that if he registers to the site mentioning the same fake id in email address box for new user then he gets the notification 'This person joined the site' and number of invitees increases in invite statistics despite the fact that id does not exist practically nobody joined the site. Still he will be among the top inviter.

Is there any way out to solve it? I am a noob so don't have much info if this is possible or not. Can we check if that mail id is fake as in mail will sent back right?

I will appreciate if anybody could give some advice how to do it?