when a mail is being send from info@example.com to yahoo mail/rediff mail since email id of yahoo/rediff is valid but they are not reaching to mail box

SMTP error from remote mail server after RCPT TO:<skd@gmail.com>:
host gmail-smtp-in.l.google.com []:
550-5.1.1 The email account that you tried to reach does not exist. Please try
550-5.1.1 double-checking the recipient's email address for typos or

Return-path: <support@example.com>
Received: from localhost.localdomain ([] helo=localhost)
by dnode1.server.net with esmtp (Exim 4.69)