My email server was changed to my domain name and as such I can’t proxy the A record for it anymore because I keep getting Reverse DNS PTR errors.
Email is working fine now but I wonder if turning off proxy on A record would affect my use of Cloudflare especially the Automatic Platform Optimization which I paid for
With the proxy off, you only get DNS, not any Cloudflare features.
Your MX record shouldn’t be pointed at your root domain. Your mail server should use another hostname, not proxied, with the MX record pointed to that.
If you look up your MX record, you will see that a synthetic record is being returned to work around your problematic configuration. Creating a different, dedicated hostname for your MTA as @i40west described is a preferable solution.