Hello,
I'm Delphi developer for more than 15 years, but I need some explanations on your questions:
1. Do you want to validate the email address if it's exist or not?
if so that's not possible, because of that you see all sites send confirmation email to the email enter to be validated.
2. Do you want to validate the input if it's valid email or not
That's can be done easily.
3. Do you want to validate the email server is valid
also this can be done by communicate with DNS or MX record to check the email server if it's exist and valid or not.
Regards,
Mohammed