This is using MS Exchange 2010. A user comes to me and told me that an external user tried to send her email but always got rejected, with the error message as follows:
One of our clients sent this delivery failure notice to us.
Technical details of permanent failure:
Google tried to deliver your message, but it was rejected by the recipient domain. We recommend contacting the other email provider for further information about the cause of this error. The error that the other server returned was: 550 550 5.7.1 Recipient not authorized, your IP has been found on a block list (state 17).
Does this sender or recipient problem? How can I get rid of it?