The bill from Cox has www.cox.com at top, but below that is the "Your bill is available" subject and below it From: Cox Communications (mynotifications@cox.com). When you print the email, the top part with www.cox.com in it doesn't print.
The reminder that your bill is due in 7 days is from Cox (no-reply@mc.cox.com)
After Cox finished a scheduled shutdown the email they sent was from Cox (residential@em.cox.com)
Wildfires and connectivity: How to Prepare was from Cox (residential@service.cox.com)
All of them were sent to my email address that is failing to receive emails sent by Cox tech support (or whoever it is that replies to my email to cox.help@cox.com.