After trying to send an email to an @live.com account, and getting a blocklist error in return, I've spent the last couple of days working on Domain PTR records, Reverse DNS, and email deliverability.
I had already set up SPF, DKIM, DMARC, and the domains PTR records. However, the error I got from the live account indicated a problem with the PTR records. So I started double-checking settings, and came across an occasional PTR record error being reported within WHM, and CPANEL. After eight hours troubleshooting PTR records, BIND9, and all things related to DNS and domain name records, I emailed the web host, and they confirmed all my settings were correct with no errors being reported. I also emailed the Live support people, and they said our server IP address wasn't on the blocklist like the error message said it was!
I'm going to give it a few days, and work on it again.