Email routing giving "521 5.3.0 Upstream error. TuhicvK1UwOp" error

I activated email routing on my domain, but I can’t seem to get it working.
All DNS options are in place, I have a catch-all forward, but I always get the following error message when sending an email

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Are you trying to send email to or from your custom domain? Email Routing only works for inbound email - you cannot use it for sending emails.

I set Email Routing on Cloudflare all @aaa.aaa sent to
[email protected]

And I send the mail test in this way:

[email protected] Send to [email protected]

then get [email protected] the error message
521 5.3.0 Upstream error.

In addition, I found that my Email Routing - Email DNS records kept spinning in circles without responding

I set Email Routing on Cloudflare all @aaa.aaa sent to
[email protected]

And I send the mail test in this way:

[email protected] Send to [email protected]

then get [email protected] the error message
521 5.3.0 Upstream error.

In addition, I found that my Email Routing - Email DNS records kept spinning in circles without responding

But I have settings in the DNS dashboard