As others have pointed out, the short answer is no. Without sending an email, you can't tell for sure whether an email adddress is valid (all email validation modules are to eliminate those that are for sure not valid.) Furthermore, even after you send an email, you still can't be sure whether it's valid, certainly not while the user is waiting. This is for many reasons, for one, it can take an indefinite amount of time to deliver/process it; second, some/many email servers will remain silent even when an address is not deliverable (to fight spam).