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�s identifying the message as spam.