Show HN: Check whether an email address exists

Email address validation is basically an impossible problem. In practice, the best strategy is:<p><pre><code> 1. Check if email is wellformed, with an *extremely* lenient algorithm. Basically, do we have .*@.* ? 2. Check that the domain is real, has an MX record, and the SMTP server in the MX record exists. </code></pre> Ok, send mail! The only way to verify after that is to send an email with a verification link and complete the circle.

Um... I hate to be so harsh but this is worthless. Checking a few of mine, all different domains, I got<p>Nemesis ESMTP Service not available 554-No SMTP service 554-IP address is black listed.<p>---<p>This domain has a catch all email address so we are unable to determine if this email matches an account.<p>---<p>Error: Invalid greeting from server - 554 No SMTPd here This email does not exist or cannot be found<p>---<p>Error: Invalid greeting from server - 554 Your access to this mail system has been rejected due to the sending MTA&#x27;s poor reputation. If you believe that this failure is in error, please contact XXXXXX This email does not exist or cannot be found<p>So... yeah... 100% error rate on something that says &quot;the results should be relatively trustworthy.&quot; Relative to what? That success rate doesn&#x27;t even crack the Mendoza Line.

Not working reliantly for me. Addresses that definitely exist are reported as not existing. No info on the checks used.<p>So, this could even just be a clever way to collect email addresses through a simple form.

Heh, we all learned to disable VRFY 15-20 years ago.<p>This fails both ways on my tests.

Nope. Reports @example.[something] as existing, whereas info@[something else] - which regularly gets mail - as nonexisting. Both Type I and Type II failures, but confidently proclaims the verdict? Worse than useless: actively misleading.

It seems that some domains just kill the backend. For my work e-mail, and probably any other on the same domain, it returns HTTP 503 (service unavailable) after ~30s, and frontend is stuck at &quot;Checking…&quot; forever. Maybe our mailserver fights back the spammers somehow. :)<p>Also, it kinda sucks that i can&#x27;t send the query with Enter key, and i bet it sucks much more for eg. visually impaired users. Is there any particular reason you used bunch of &lt;div&gt;s instead of good old &lt;form&gt;?

We use Cisco&#x27;s cloud Ironport solution for email spam protection and I get the following when I check my email address: Error: Invalid greeting from server - XXXXXXXXX.iphmx.com 554 Your access to this mail system has been rejected due to the sending MTA&#x27;s poor reputation. If you believe that this failure is in error, please contact the intended recipient via alternate means.

A link to an &quot;how it works&quot; article would be nice.

So it failed on my dynamical created email addresses<p>I have a system where i have double wildcard so X@X.some.domain and your site fails<p><pre><code> Error: Spam detection in use This email does not exist or cannot be found</code></pre>

Worked for my person email attached to my domain. I agree with others in that explaining how this works would be very nice.

Am using namecheap&#x27;s email service for my personal email and domain, this says it is an invalid email address

Yea this has not validated an email for me. Tried a few email clients and nothing said it was valid.

This is cool but yea some right up would be appreciated.