Evan,
Thanks! This gets me much farther down the road.

For others that might be following this thread, I've included email-screen's white paper on e-mail address validation. Here is the link:

http://www.email-screen.com/Email.Validation.Whitepaper.doc

Notes on Levels of Validation

Base Level Validation - This is the type of email validation that most current web sites use. This is extremely inadequate and needs to be upgraded. The reason that most sites use this method is that it is easy to code.

Base Domain Level Validation – This email validation is a step up from Base Level Validation, but still extremely inadequate. This level of validation only requires that the domain name of the email address be a valid registered domain. Many domain names are registered but cannot receive email. Additionally, the majority of registered domain names are not currently active mail servers.

MX Domain Level Validation – This email validation is currently the highest feasible level. It is not 100% foolproof, but is a marked improvement over any lower form of validation. This level guarantees that the domain name of the email address is not only registered, but also that it is a live Internet host that can actually receive email. This is the base competitive level of email validation.


Absolute Validation – This is a theoretical level of email address validation. In this level, email addresses could be validated with 100% accuracy. Currently, this is nearly impossible to achieve. Internet servers run various operating systems which handle email in various ways. Additionally, due to security considerations, many operating systems are configured in such a way that specific email account validation is impossible. Although this is theoretically the best, it is functionally impossible.

>>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