.con might be a valid TLD though, there's so many TLDs now.
Just send a verification email...
Just send a verification email...
https://mandrill.zendesk.com/hc/en-us/articles/205583217-Int...
Wouldn't integrating this help solve the issue, as you can possibly check if you received a bounce for that email shortly after the user attempts to register, and then notify them on the screen?