>What is the best way to validate that e-mail addresses are deliverable? I'm not talking about checking the formulation of the address (name@somedomain.com) but rather getting a response back from a mail server that the address is valid.
>
>I could process the delivery confirmation messages by sending an actual message, but I'd prefer NOT to send an actual message to the addressee, if possible.
>
>Anyone know if (and more importantly how) this is possible?

I thought this was impossible but I found this on Google.

"A web site developer need only feed EmailScreen a DNS server and an email address; EmailScreen will return a true or false, based upon the results of testing."

http://www.xpresspress.com/news/emailscreen_082800.html