

How to Verify an Email Address - DatFemmeFatale
http://blog.online-domain-tools.com/2014/11/14/how-to-verify-email-address/

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DZittersteyn
This is answering the question: "Does tihs email address exist?", which is
nice, but usually not the question being asked. The more common question is
"Is this the email address of the user", which can only be answered by a
confirmation email.

You could use this method as a first-line validation though, to give the user
some feedback (similar to not implementing the full RFC regex, but simply
checking /.+@.+\\..+/)

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laurencei
Maybe I missed it - but what is stopping spammers from using this technique on
their email lists to check they are all correct?

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vidarh
Nothing, but it's also too slow, and pointless for them: It's easier for them
to just send. Many of them clearly don't even care about checking response
codes, or retry after greylisting, which is why these techniques works
(greylisting cut our spam volume by about 90% off the bat).

But there's also _no guarantee_ that the remote server will reject the address
until after you've actually submitted a full e-mail, and send the final "." ,
exactly to make it even more expensive for spammers, in which case any attempt
at checking short of actually sending an e-mail will fail.

Their suggestion _may_ give you an indication, but if you try to rely on it
you'll get a lot of pissed off users.

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cr3ative
Wouldn't this choke if the user's mailbox was full?

I understood the default generic answer to this was "send an email to it,
through a mailing service you pay for, not through your own infrastructure."

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drinchev
Actually I think the default answer for this is "Send a confirmation link to
the email", because you skip almost all the impossible edge cases, like
"catch-all address" or using public e-mail address or whatever.

Most important question you have to ask yourself is "What do I want?". If the
answer is "This user e-mail address.", there isn't better way than sending a
confirmation email.

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vidarh
Absolutely. There simply _isn 't_ a reliable lookup method.

As I pointed out elsewhere, there are plenty of e-mail systems that won't tell
you whether or not the address exists until _after_ you've submitted a valid-
looking e-mail anyway.

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darklajid
Or .. don't.

Send a mail. If it bounces, ignore that. If someone takes an action based on
the content of the mail you sent, the address is valid. I'd say this link is
bad advice.

