We haven't been able to deliver the message to the recipient yet. When we tried delivering the message, your organization's ...

We haven't been able to deliver the message to the recipient yet. When we tried delivering the message, your organization's mail server responded with a temporary error. Please review these details:

Recipient: {Recipient}
Email server name: {DestinationMailServer}
Connector name: {ConnectorName}
Technical error message: {MessageDetail}

To fix the problem, we recommend that you verify your connector settings before troubleshooting your DNS configuration.
Go to the connector page.
Choose the connector indicated in the previous section, and choose Edit
Check the connector configuration for typos or wrong information.
If that doesn't fix the problem, you need to fix the issue on your organization's email server based on the error in the previous section.

We'll keep trying to send the message for a total of 48 hours. After that, Office 365 will stop trying to send the message and will return a non-delivery report (NDR) to the sender.