Email routing failed

Rejected reason:
Unknown error: permanent error (521): 5.3.0 Upstream error, please check for possible reasons why. CfoJA4eGFJWV

SPF status

DMARC status

DKIM status

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