How To Check If A Name Is Registered

We accept all been doing electronic mail address validation for a very long time to brand certain that the email is correctly formatted. This is to avoid users entering wrongly formatted email address but still they can accidentally requite usa a wrong email address.

Instance of a correctly formatted email address but still incorrect:

mailbox.does.not.exist@webdigiapps.com [VALID format but does not exist]

Above example specifically happens when you take important client electronic mail on phone and you type in the wrong electronic mail. And then is in that location a QUICK solution to actually cheque the email without sending a test message to the user? Yes.

How to test if the email address really exists

To check if user entered email mailbox.does.not.be @webdigiapps.com really exists go through the following in command prompt on windows / terminal on mac. The commands you type in are in dark-green and the server response is in bluish. Delight refer to MAC & PC screenshots towards the end of this post.

Footstep 1– Detect mail exchanger or post server of webdigiapps.com

Command:
nslookup -q=mx webdigiapps.com
RESPONSE:
Non-administrative answer:
webdigiapps.com mail exchanger = 0 mx2.sub3.homie.mail.dreamhost.com.
webdigiapps.com postal service exchanger = 0 mx1.sub3.homie.mail.dreamhost.com.

Pace 2– Now we know the mail server accost and then permit united states connect to it. You can connect to i of the exchanger addresses in the response from Step 1.

Control:
telnet mx2.sub3.homie.mail.dreamhost.com 25
RESPONSE:
Connected to mx2.sub3.homie.mail.dreamhost.com.
Escape grapheme is '^]'.
220 homiemail-mx7.one thousand.dreamhost.com ESMTP

COMMAND:
helo how-do-you-do
RESPONSE:
250 homiemail-mx8.g.dreamhost.com

Control:
mail from: <youremail@gmail.com>
RESPONSE:
250 ii.1.0 Ok

COMMAND:
rcpt to: <mailbox.does.not.be@webdigiapps.com>
RESPONSE:
550 5.1.one <mailbox.does.not.exist@webdigiapps.com>: Recipient address rejected: User unknown in virtual alias table

Command:
quit
RESPONSE:
221 two.0.0 Bye

Screenshots – MAC Last & Windows

NOTES:

ane) the 550 response indicates that the email accost is not valid and y'all have defenseless a valid just wrong email address. This code can be on the server and called on AJAX when user tabs out of the email field.  The unabridged check will accept less than two seconds to run and you can make sure that the email is correct.
ii) If email was nowadays the server will respond with a 250 instead of 550
3) There are sure servers with a CATCH ALL email and this means all email address are accepted as valid on their servers (RARE but some servers do have this setting).
four) Please exercise not use this method to continuously to check for availability of gmail / yahoo / msn accounts etc every bit this may crusade your IP to be added to a blacklist.
five) This is to supplement the standard email address javascript validation.

Source: https://www.webdigi.co.uk/blog/2009/how-to-check-if-an-email-address-exists-without-sending-an-email/

Posted by: pendletonplebadve.blogspot.com

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