Email Recipient Validation

[tonex]

How do I check if the email recipient is truly existing and active when using the mail() function in PHP?

For example, a user must provide the page his email address in order for the page to process something the user wants. How can PHP check if the email address the user provides is actually active and existing?

Thanks.

[Anon]

send him an email and make him reply to it to proceed or click on a link inside the email to proceed.

[tonex]

The objective of my script is to just check whether the user gave a valid email address. The user should not be involved in the validation since the integrity of the information he/she gave is the one being validated.

[Anon]

You may be able to finger the user at that domain but not all domains allow this and even if it came back saying it was ok. That doesnt meen he gets email there. To my knowledge aside from sending them an email there really is no way to know.