Cox Censorship? Reopened!

Previous post, with title "Cox Censorship?" (from April 2019) was closed after a non-answer posting from a Cox rep. I have had the exact same problem today, and it is not going away by itself:

(1) I try to send an extremely short email, from my MacOS Mail account, via the Cox SMTP server, with the "From" address as any of my 3 Cox email addresses, with the format XXXXXXXX@cox.net. Note that my Mail installation has been configured to send and receive email via all 3 Cox accounts/addresses since I bought the iMac in January 2020.

(2) That short email contains the word "TEST", followed by whitespace, followed by a valid URL for a local business (FORMATTED AS PLAIN TEXT) which I am certain is not on ANY VALID BLACKLISTS as spammers, followed by more whitespace, and finally by another word "TEST". The subject of that email is "TEST", and the target address is XXXXXXXXXX@gmail.com. The plain-texted URL is "hascosb.com".

(3) As described in the closed email, Mail thinks awhile, shows a sending progress bar, and then pops up a dialog stating that Cox rejected the message, EXACTLY THE SAME AS IN THE POSTING CLOSED AFTER COX DECLINED TO ADDRESS THE PROBLEM:

"The server response was: <xxxxxxxxx@cox.net> message rejected. Refer to Error Codes section at https://www.cox.com/residential/support/email-error-codes.html for more information. AUP#CXSNDR" (Obviously, "xxxxxxxxx" replaces my actual user name, as it did in the original post.)

A bunch of experimentation demonstrates irrefutably that some service (probably malfunctioning or poorly-written security) running on Cox's SMTP server is solely responsible for this unnecessary and inane failure:

(1) I can order Mail to send the exact same email without the URL from any of my Cox addresses (ie using Cox's SMTP server), and the email goes through to the target Gmail address.

(2) I can order Mail to send the exact same email WITH the URL from my GMAIL address (ie using GOOGLE's SMTP server), and the email goes through to the other targeted Gmail address.

(3) I can order Mail to send the exact same email with the URL DISGUISED ("xyzhascosb.comfgh") from any of my Cox addresses (ie using Cox's SMTP server), and the email goes through to the target Gmail address.

Clearly, Cox's security service(s) is(are) searching through my emails for URLs that Cox has, for some obviously invalid reason, chosen to blacklist, and then refusing to send the email.

I, like most Cox customers in the Santa Barbara/Goleta area, am paying ridiculously high monthly fees to Cox for this kind of poor service. Functional email is one of the services that Cox is supposed to provide for those exorbitant monthly fees. The ignorant, irrelevant responses posted by, and premature closures imposed by, Cox reps to complaints like mine today, indicate how little Cox cares about providing adequate service to the customers of the monopoly granted to Cox by the cities of Santa Barbara and Goleta.

In the anticipated absence of a cogent, productive reply from Cox's actual tech support department, it would seem that the only recourse I (and others experiencing the same persistent, uncorrected failures in Cox's email service) have is to stop using my Cox email addresses, in favor of a different provider (like Google). The downside of this approach is that we pay Google for the service by allowing them to scan our emails and sell the gathered info to advertisers. However, Google does provide relatively accurate spam filtering, so when I get spam (possibly from entities to whom Google sold my preference info), I just block it manually if Google doesn't block it automatically.

Generally, Google's email service is MUCH faster (through Safari, Firefox, Mail, and Thunderbird), and has not yet refused to securely send an email containing a URL that is not on any general blacklist for any good reason.

I hope that Cox proves me wrong about simply declining to address or fix the problem properly before closing or removing this post.