As far as I understand, this is an error on the RECEIVING END, (Exchange server) and not the SENDER. It's not that clear in the link You posted, I must admit.
The receving mailserver is an MS-Exchange, and the on-line guide describes how to fix the problem in MS-Exchange.
You route all incoming mail for your hybrid domain through Exchange Online.
This error can happen when the MX record for your hybrid domain points to Exchange Online, and the Outbound connector that's used to route mail to your on-premises Exchange organization is configured to use DNS routing.
To fix the problem, configure a dedicated Outbound connector that uses smart host routing and that has your on-premises hybrid server configured as a smart host. The easiest way to fix the problem is to re-run the Hybrid Configuration Wizard in the on-premises Exchange organization. Or, you can verify the configuration of the Outbound connector that's used for hybrid by following these steps:
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