Without making any DNS changes, the 521 errors are gone.
Although catch-all forwarding is active and no DNS errors are reported, no email is being forwarded, but is going directly to my mail host at Hostgator.
If I try to send email to an addresses which does not exist on my mail host I get a “No such user here” response.
Email validation test confirms the Cloudflare exchangers are seen.
What must I change to get forwarding working?
Thanks all,
UPDATE
Email forwarding IS working, but ONLY from accounts not hosted on the same server which previously hosted the email for this domain. It looks like mail from other co-hosted domains is routed internally at the host site, without going through Cloudflare!
Go to cPanel and look for the Mail section then proceed to the Email Routing tab from the drop down menu choose the domain name affected and then choose Remote Mail Exchanger for the domain and then hit change.