Years and years ago (2000, I think), I implemented a script in PHP that
allows us to test whether our server will be able to deliver to an email
address. It's based on some code by Jon S. Stevens <jon(a)clearink.com>
(google that + "validateEmail" and you'll find examples). It first does a
DNS lookup for the MX record, then if that's successful it attempts a
standard SMTP HELO/MAIL FROM/RCPT TO/QUIT sequence and checks for errors in
the mail server's response.
If you have some familiarity with PHP, I'd be happy to send you the version
I wrapped into a function which you could easily loop through. The RFC822
class from PEAR could help process the text file for addresses. Or perhaps
someone here knows more about how to do it in python. Such a utility could
make a slick addition to the admin page in version 3.
There are also commercial tools to do this.
dave(a)aasv.org ; webmaster(a)aasv.org
If there's a service or utility that can verify a list of email addresses
(prior to a mass operation), please suggest it.