Again 521 5.3.0 Upstream error

It seems that after first setup of Email Beta - for catch-all address there is some error.
It looks the same as in:

The specific addresses works crrectly - not sure about catch-all one…

Some message:

Status: 5.3.0
Remote-MTA: dns;
Diagnostic-Code: smtp; 521 5.3.0 Upstream error. 5jvzKYghrqab

I have a similar issue with the error message
but cannot post here as it said “Sorry, new users can only put 4 links in a post.”

Hey! I am also facing the same error.

Facing the same issue. Anyone get help from support or any other info to diagnose the underlying issue?

Hi Anyone,
Did you get any solution for this error?
Since I am getting same error with one of my domain.
Please help me out if anyone of you have any solution for this

No, I had to switch away from using Cloudflare for email sending for the affected domain, as I was unable to solve the issue. I think there are paid products that are taking the place of this offering, so there is little engineering/support effort. It does work for receiving email though, so there are still some use cases that make sense.