Business email address blacklisted as spammer
I figured it out. Someone just happened to tell me that extra spam protection DNS records had not been set up for my business email account. While looking that over, Office 365 indicated that my SPF record was incorrect. I had not changed it. However, when my website hosting provider moved my account and web page to a faster server and changed the DNS records to match that new server, he mistakenly put his email server's SPF record in place of my correct Office 365 SPF server. That made Cox think I was not a legitimate email account since I was sending from Microsoft, but my SPF record was from another email server. I changed the SPF record to Microsoft's correct information and my emails now go through to Cox. It would have be nice for Cox to have just said, hey, your SPF record is incorrect.
I thank everyone who gave help at the forum. It was appreciated.