Are you trying to send a confidential email message to your boss, friends, acquaintances and so on before making it do an email id check whether the email address that you have entered while composing is really exists and live or not? Because the email ID associated with an account might be deleted from the server (or) even a single incorrect alphabet letter (or) numbers(i.e.typos) will never let the email-server to deliver email to the recipient address with typos which eventually returns as "Failure Notice". Sometimes email server takes hours to notice its failure to deliver the mail to that particular email ID because whenever an email is composed and sent, the email server makes several possible attempts to reach the recipient's mail ID. So you may think that your message has been sent and delivered to that particular address but actually, it wasn't delivered. See Also: How to create multiple twitter accounts with same email ID How to Instantly Check If a...