Mail routing errors


I have a Custom Address route set up to forward emails from one email address to another, both on the same domain.

When I send to the address to be forwarded, I am getting bounce errors like this:

The response from the remote server was:
521 5.3.0 Upstream error, please check for possible reasons why. pRhrLCl8HYb6

In the CF Email Routing Summary, I’m seeing this:

SPF status


DMARC status


DKIM status


Rejected reason:

upstream (.) error: failed to initalize: Unknown error: permanent error (550): 5.1.1 Address does not exist. LLmeRiawaJpq

What’s odd is that I’ve tested sending to this email address from three different domains. Two failed (bounced) and one worked perfectly.

Any thoughts or suggestions?

Thank you.

Can someone please help me with this?
Thank you.

Are you forwarding one address to another address at cloudflare?
if so, don’t do that, forward to the actual external destination address.