The message could not be delivered because the recipient's domain doesn't have a valid MX record in DNS. Please review these ...

The message could not be delivered because the recipient's domain doesn't have a valid MX record in DNS. Please review these details:

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

To fix the problem, we recommend that you check the recipient's address to see if there is a typo.
If that doesn't fix the problem, you'll need to ask the recipient's admin to fix the DNS configuration. The recipient domain must have a valid MX record in order for Office 365 to deliver the message.

Note, we sent a non-delivery report to the sender that gives the details about why the message couldn't be delivered.