email address validation, how to?

Question

I'm validating email addresses in a c# app, beside the regular expression I'm planning to add some advanced validation by communicating with the mail exchanger and get a response whether such email address exists or not

does any one has a good idea of doing that ? i know a website that can check it :

http://www.ip-address.org/verify/email-checker.php

but I'm not sure what is the approach the website uses for validation. i tried emulating a telnet session on my mail exchanger and then sending commands

MAIL FROM and RCPT TO

but it doesn't work, either the connection is blocked, or the response is erroneous

Whatever other answers you get, **please** don't write your own. — hcarver, Aug 22 '12 at 16:21
@Hbcdev : you mean, real names, IPs...of course not, but thanks for the reminder — user1327073, Aug 22 '12 at 16:28
Did you search SO? http://stackoverflow.com/questions/1365407/c-sharp-code-to-validate-email-address might be useful. — hcarver, Aug 22 '12 at 16:31
thanks, but it seems like a real issue...everywhere :), think i'm going to stick with my regex for the moment. — user1327073, Aug 22 '12 at 18:19

score 0 · Answer 1 · answered Sep 15 '14 at 21:25

The technique you describe no longer works and variations on it don't work either-- the mail server will respond incorrectly or mark you as a spammer, ref. http://www.spamresource.com/2010/11/smtp-address-validation-bad-idea.html

Mail-Bee NET has some features like this and the documentation says it can work, but you need to convince the other mail servers that you are also a mail server. http://www.afterlogic.com/mailbee-net/docs/getting_started_with_address_validator.html

Either way, it sounds like a risky project and likely to get your mail server blacklisted.

email address validation, how to?

1 Answers1