Email Routing is not working when using catch-all.
Same as this case.
▷ Email Routing not working when using catch-all - DNS & Network - Cloudflare Community
If the domain is “example.com”, emails sent from *@example.com arrive normally, but emails sent to *@example.com don’t arrive normally.
Remote Server returned '521 5.3.0 Upstream error. Rg7jEX0XHP3s'
@MoreHelp My ticket number = 2438251
Okie I have one solution for you , emails sent to your domain dont arrive , this means email forwarding is not active on your domain name , you can use a free forwarder called improvmx.com which allows you to create free email forwards , let me know if you have any other doubts