You can only find out whether a mail to an address arrives somewhere by sending a mail there.
Not even not receiving a non-delivery message proves that the mail arrived. It can be dropped without message to you.
Without sending a mail, you validate the address format. Like exactly 1 @ in it. At least one dot right of the @, but not at the end. No forbidden characters, and so on.
Also you can check if the part right of @ is an existing mail domain. But I think this is useless work, because you will have mostly addresses like hotmail.com.