521 5.3.0 Upstream error

Hello Cloudflare-Community,
i have a problem with Cloudflare E-Mail (Beta).
i have the same Error: Email routing giving "521 5.3.0 Upstream error"

Another domains working without any problems.

All another Domains: Any E-Mail Account/Provider —to—> Any [email protected] —forward—> [email protected] = Working/Received

example.io : Any E-Mail Account —to—> Any [email protected] —forward—> [email protected] = not working/not receiving

BUT if i change [email protected] to [email protected] or [email protected], it’s working

example.io : Any E-Mail Account —to—> Any [email protected] —forward—> [email protected]/ [email protected] = Working/Received

Only one domain is not working with a specific adress [email protected]

Any idea, why this domain with the same settings/szenario and address is not working?
I can send my domain via PM, if u want.

SMTP error from remote server for TEXT command, host: amir.mx.cloudflare.net ( reason: 521 5.3.0 Upstream error. fr3pl98HNKBx

Thank you

Can someone help me?

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.

Hi morekula154,
i feel with you and im so sad you have the same problem.
I give up, i tried so many things, and last month i give up. Moved some domains away from Cloudflare i found no solution and nobody helped (Support/Community).
If you find with your luck a fix for this bug, please please please tell me :slight_smile:
I wish you much success on this rocky path.

I also not able to find anything yet…
I tried by contacting Cloudflare support also. But they are also not able to find the exact solution.
Yes definitely I will share if I found anything.
Meanwhile can you please let me know if you have any good alternative of Cloudflare or any mail forwarding application which works with any error

For free?
If yes:
Not rly, idk any good choose.
For mail forwarding (receive ->forward) Mybe something like : Private geschäftliche E-Mail - Kostenlose professionelle E-Mail | Forward Email or Private geschäftliche E-Mail - Kostenlose professionelle E-Mail | Forward Email

For sending (SendGrid , MailJet , https://de.sendinblue.com/ )

any updates?