How long can a TLD possibly be?

Question

I\'m working on an email validation regex in PHP and I need to know how long the TLD could possibly be and still be valid. I did a few searches but couldn\'t find much infor

Answer 1

A TLD can be any length at all. New TLDs happen all the time. In the future there will be more TLDs not regulated by the entity currently regulating the majority of TLDs. We also won't use email in the future as we presently do. That said:

You don't need to validate an email address ever. If you want to slow people down and have an idea as to whether they're actually human, include a CAPTCHA. If you need to confirm working email, send an email with a validation link they can open. If you aren't throttling submissions of things that can generate things like emails being sent for verification, it won't matter whether you're confirming the address is technically valid anyway, it will be abused at that point regardless.