How to find out Invalid Email Address without send? Just check all Email Address.That is already possible: https://xenforo.com/community/threads/automated-bounce-email-handling.78137/
Members with bounced (invalid) email addresses will see a notice the next time they log in.
Server IP are goes block from RBL if email sending Failed and bounced. Please look here: https://documentation.mailgun.com/api-email-validation.html#email-validationHow to be sure an email adress is incorrect without sending a mail to it?
gmail.com is known mail provider = auto corrected
xenforo.com just a domain. So check its mx values but how to know email@example.com is reachable, or not, without sending mail?
My opinion, it is not possible