Here are a few links that I found that show how to validate the e-mail
address provided by checking with the recipient's server:

http://www.webdigi.co.uk/blog/2009/how-to-check-if-an-email-address-exists-without-sending-an-email/
<http://www.webdigi.co.uk/blog/2009/how-to-check-if-an-email-address-exists-without-sending-an-email/>
http://www.barattalo.it/2009/12/27/validate-email-with-smtp/
<http://www.barattalo.it/2009/12/27/validate-email-with-smtp/>
http://onwebdevelopment.blogspot.com/2008/08/php-email-address-validation-through.html

<http://onwebdevelopment.blogspot.com/2008/08/php-email-address-validation-through.html>--
Rob

On Tue, May 25, 2010 at 9:16 PM, Rob Scott <[email protected]> wrote:

> To test if an e-mail address is "legitimate" could mean a few things:
>
>    1. That the e-mail address *syntax* is correct - meaning that the
>    address entered is valid per the RFC that sets guidelines for such things.
>    This article looks useful for determining is an e-mail address
>    is syntactically correct using PHP:
>    http://www.linuxjournal.com/article/9585
>
>    2. That the e-mail address is actually real - meaning you could send an
>    e-mail to it and it would be accepted. The only way to do this would be to
>    create a program that connects to the mail server responsible for handling
>    mail for the address provided, and seeing how it responds to the RCPT TO
>    smtp command. If the server responds with a positive acknowledgement to 
> RCPT
>    TO (250), then it is telling you that it will accept mail for that
>    recipient. Unfortunately, this is not always 100% accurate - some servers
>    will accept mail for *any* address at their domain, and then bounce the
>    message asynchronously. Microsoft Exchange servers are typically setup to
>    handle mail this way by default, but can be configured to reject
>    the recipient during the SMTP conversation. I imagine that someone has 
> built
>    an e-mail address validator that does this, but I couldn't find any by
>    briefly searching on Google.
>
> HTH,
>
> -- Rob
>
> On Tue, May 25, 2010 at 7:25 PM, Luis Torres <[email protected]>wrote:
>
>> As Dan pinted out this is not possible anymore for remote hosts.
>>
>> Depending on permissions it might be an option for local accounts in a
>> *nix system but checking might only add complexity to your task so I'd steer
>> away from it.
>>
>> Good luck,
>>
>> LT
>>
>>
>> On Tue, May 25, 2010 at 5:31 PM, Dan Brown <[email protected]> wrote:
>>
>>> My understanding is that what you're looking for isn't available any
>>> more. You used to be able to send a command to a mail server and get a
>>> response back indicating if the address was valid or not. Spammers caught on
>>> to that, however, and abused it to farm addresses, so most email servers now
>>> ignore the command. You may have luck with some older mail servers, but it's
>>> definitely not 100% reliable.
>>>
>>> -db
>>>
>>> Dan Brown
>>> db interactive Inc.
>>>
>>>
>>> dmmontana wrote:
>>>
>>>> I have a client with an e-mail sign-up form on their site. In addition
>>>> to validating the syntax, they want to be able to determine on-the-
>>>> spot if the entered e-mail address is legitimate. I've come across a
>>>> couple of forms recently that do that but I can't remember where they
>>>> were.
>>>>
>>>> I did find the following PHP code:
>>>> http://code.google.com/p/php-smtp-email-validation/
>>>> . However, I haven't been able to successfully implement it (I'm a
>>>> front end developer, not a programmer, and nothing I've tried has
>>>> worked). Has anyone had any success with this or another solution?
>>>>
>>>> Thanks!
>>>>
>>>>
>>>
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