Error code when forwarding emails

I've been trying to forward emails which are about something that I ordered to someone, but I keep getting a rejection error which says: "message rejected. Refer to Error Codes section at www.cox.com/.../email-error-codes.html for more information. AUP#CXSNDR"

Why? The emails that I'm trying to forward aren't spam and the email address that I'm trying to send to is valid. Cox, please fix this!