Verify the existence of email id

We can verify the existence of email address using some Linux commands.

For example here we are verifying the mail-id user@example.com

Step1: Find mail server of domain example.com.

#dig mx example.com

Let the mail server of example.com as mail.example.com.

Step2: Connect to the mail server using telnet command as follows.

telnet mail.example.com 25
Connected to mail.example.com.
Escape character is ^]
220 mail.example.com ESMTP
helo
250 mail.example.com
mail from: <user@example.com>
250 2.1.0 Ok
rcpt to: <admin@techies-world.com>
550 5.1.1 <admin@techies-world.com>: Recipient address rejected: User unknown in virtual alias table
quit
221 2.0.0 Bye

Please note that we could not assure 100% result in this method as some mail providers like hotmail.com, live.com are blocking these kinds of email verification process.