Office 365 received the message that you specified. Unfortunately, we couldn't deliver the message to the recipient ({0}). ...

Office 365 received the message that you specified. Unfortunately, we couldn't deliver the message to the recipient ({0}). This is either because we couldn't connect to the recipient server or the recipient server returned a temporary error. We kept trying to send the message for 48 hours, but finally gave up. Details are in the following section.