Email exist verification

Is it possible to check if an email-address is exist开发者_高级运维ing?

I have earlier heard that it was possible through "contacting" the email-host, but it could be "dangerous" because your domain could be banned by the respective email-host an treated as spam.

My scenario is that i would like to check customers current email in the db, and update if needed.

What option do i have?

I'm using ASP.NET with MVC.

Thanks, Michael.

AS per the email address itself, you can check that the domain exists (DNS wise) and has MX records. This is a way to check - roughly - the human mistakes while inputing the email in the first place. You may catch a few percents.

If you need a serious check of all the users/clients, and this is mandatory, the only solution I see is to send them a mail asking them to click a link in order to validate their account.

But your mail may be taken for spam / a way to steal information, and many users may be afraid to actually click. So your mail must be carefully constructed, indicating the name and firstname of the person (less likely to be spam) and the reason why you need absolutely some help from their side.

Yes, in SMTP you can resolve MX record for the recipients domain and then contact the given server and do a RCPT TO: - the server will then confirm / deny whether the recipient exists (assuming that the server will refuse to RELAY and that the server won't do catch all)