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

Office 365 received the message that you specified. Unfortunately, we haven't been able to deliver it to the recipient ({0}) yet. We can't deliver the message because Office 365 can't connect to the recipient email server. It looks like your remote server's firewall is blocking the message from Office 365 because it is identifying the message as spam.