Re: email validation

by Ilya Dubinsky <ilya788(at)inter.net.il>

Date:	Fri, 14 Jul 2000 12:41:27 +0200
To:	Andrew Browne <andrew(at)pbm.co.za>
Cc:	hwg-languages(at)hwg.org
In-Reply-To:	ANDREW
	todo: View Thread, Original


>Hi all
>
>Is there any means of an IIS4 server checking whether an email is 
>valid?  By valid, I don't just mean whether it conforms to the 
>here(at)there.com naming convention, but whether here(at)there.com is an email 
>address that actually exists in reality.

         You can do the following (I haven't seen it in NT means, but there 
is a PHP script somewhere around php.net):
         1. Extract domain name
         2. Do a DNS query of type MX to extract mail exchanger for the domain
         3. Connect to the mail exchanger
         4. After "HELO" SMTP handshake, issue a VRFY user, where user is 
the before-@ part of the email.
         5. Examine the error code of the answer. (note, that some SMTP 
mailers, QMail, for instance, do not allow VRFY command and so, all 
attempts to validate email addresses when MX runs QMail will fail.

         Or, alternatively, you may send an email message to the address 
and wait for email to bounce (this is much more time consuming, but it works).


>Thanks in advance
>_____________
>Andrew Browne
>IT
>658-6484
>_____________

				Yours, Ilya.

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