When you are sending emails to others and get a bounce back error message from mailer-daemon@, the error message will provide you with the error type. The most common type of errors that we see for outbound emails are email error 513, 550, and 553. Below is a brief description of what they are and what you can do to fix the error.
|CODE||WHAT IT MEANS||WHAT TO DO|
|513||Address type is incorrect": another problem concerning address misspelling. In few cases, however, it's related to an authentication issue||Doublecheck your recipients' addresses and correct any mistake. If everything's ok and the error persists, then it's caused by a configuration issue, please create a support ticket request at this point.|
|550||It usually defines a non-existent email address on the remote side||The great majority of errors 550 simply tell that the recipient email address doesn't exist. You should contact the recipient otherwise and get the right address.|
|553||"Requested action not taken – Mailbox name invalid". That is, there's an incorrect email address into the recipients line.||Check all the addresses in the TO, CC and BCC field. There should be an error or a misspelling somewhere.|