After attempting to send an e-mail, you may encounter what it known as a bounceback e-mail. It is also known as a non-delivery report, failed delivery status notification, failed delivery message, or a number of other names, or even simply as a "bounce."
There may be a number of reasons why you receive such a message, but the most common is due to a 550 error. A 550 error is usually encountered because the recipient's e-mail does not exist, although there can be other resons. You must check the bounceback e-mail for the error code, as well as the message immediately following. Two common examples of 550 error messages are given below.
This error usually indicates that the e-mail address that was supposed to receive the message does not exist. In this case, it suggested to check the spelling of the recipient's e-mail address. Typically the recipient's e-mail address was accidentally mispelled, and the mispelled e-mail address does not exist. Therefore the e-mail cannot be delivered.
This error indicates that there is a misconfiguration with the MX (Mail eXchange) record. The MX record is a DNS record which directs incoming mail to the proper mail server. The improper configuration could be the fault of the sender of the e-mail, or the intended recipient of the e-mail. Both should check to ensure that the MX record is NOT configured to use a CNAME (also known as an alias), otherwise the mail will not be deliverable.