Business email address blacklisted as spammer

Hello. I have a business email that I have used for over 20 years. Two Months ago, Cox blacklisted it as a spammer. I only send legitimate emails and when I send those communications to my Cox customers, they don't go through. I can't even send personal emails to my dear 80+ year old widowed mother any longer. I have also been a Cox customer for 21 years, having signed up with Roadrunner which was eventually purchased by Cox. That is to say, I have been a very long and hopefully valued customer and would like help.

So far, I have contacted your tier 1 support twice and they have been of no help. They read from a script and tell me over and over that you have stringent spam policies. But if I send a plain text email with only the word TEST in it, it is still blocked as spam. That means that Cox has blacklisted my email address. I have emailed to thisisnotspam@cox.net and that didn't help.

I can email to every other customer other than Cox listed emails, so this is ONLY and definitely a Cox issue.

I need to know the correct and proper process that Cox has in place to UNblacklist email addresses that were mistakenly blacklisted. As a legitimate business owner and long time valued Cox customer, I expect a prompt and successful response. Thank you.