This is so weird. I have had people say they have tried to send me emails and have not received anything. So, I sent myself a test email is this is what is sent back "*** ATTENTION ***

Your e-mail is being returned to you because there was a problem with its
delivery. The reason your mail is being returned to you is listed in the
section labeled: "----- The delivery status notification errors -----".

The line beginning with "Diagnostic-Code:" describes the specific reason
your e-mail could not be delivered.  The following lines contains the
RFC822 header of the original email message.

Please direct further questions regarding this message to your e-mail
administrator."

What does this mean? Thanks