Verifying an email address exist in C#

Question

Regarding this post about email verification,

using C#, how would you

1. issue a VRFY command
2. issue a RCPT command

Answer 1

I think you will find that in many instances these functions will intentionally lie to you to defeat spammers. If there were a way to confirm an email is real other than having a user click on a validation (or unsubscribe....) link then spammers would be very happy people.

Just to be clear, the best way to verify an email address is to send a user an email containing a link, and wait for them to click on the link to verify they received the email. Any other technique (with the exception of a corporate/intranet environment) should fail and/or lie to defeat spammers.