550 5.7.54 SMTP; Unable to relay recipient in non-accepted domain

Question

I have an Exchange 2019 Server.

I had a client tell me today that when he sends me an email it is bounced back to him. He uses AOL.

I logged into my gmail account and send a test message to my exchange email. sure enough it was bounced back with the following error message:

Your message couldn't be delivered to myemail@mydomain.us because the remote server is misconfigured. See technical details below for more information.

The response from the remote server was: 550 5.7.54 SMTP; The response from the remote server was: 550 5.7.54 SMTP; Unable to relay recipient in non-accepted domain

I am able to send email with no issues to my gmail, outlook and yahoo accounts. The issue seems to be with just this account. In addition to the email address from the domain, it also has a second email address different from the domain.

For clarity. My Windows domain being mydomain.us, the first email address is ******@mydomain.us, the second email is ******@domaintwo.us. The ******@mydomain.us,works, ******@domaintwo.us does not.

All necessary DNS(MX and A) entries are correct.

I recently upgraded to Exchange 2019 and installed Exchange anti-spam features. I wonder if it could be related to that.

Anybody have an idea what the issue is and how I can fix it?

Answer 1

Hi @Kevin,

The ******@mydomain.us,works, ******@domaintwo.us does not.

Do you mean if external senders send to user@domaintwo.us, they would get the NDR (error or bounce) message 550 5.7.54 SMTP; Unable to relay recipient in non-accepted domain.

While if sending to user@mydomain.us, the email can be received correctly.

If this is the case, what is the accepted domain setting on your Exchange server?

Please make sure you have the domain in the error message added as an accepted domain (Authoritative domain).

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If the above suggestion doesn't help with this issue, besides the accepted domains, please also post the following setting of the affected mailbox:

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