reporting spam

Often when I try to report a spam email, I get this message in my webmail page::::  Message could not be sent to the following recipients: [stop-spoofing@amazon.com] (550 - 550 message rejected.  Refer to Error Codes section at https://www.cox.com/residential/support/email-error-codes.html for more information.  AUP#CXSNDR)  :::I looked that up and it doesn't seem to relate,,,,this is a valid email address I am sending the report to.   How can I get past it to report to the proper site?