Email routing failed

Rejected reason:
Unknown error: permanent error (521): 5.3.0 Upstream error, please check https://developers.cloudflare.com/email-routing/postmaster for possible reasons why. CfoJA4eGFJWV

SPF status
pass

DMARC status
pass

DKIM status
neutral

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

Not found any solution yet

Does the community tip help? This is what Error 521 is supposed to mean: Community Tip - Fixing Error 521: Web server is down