We haven't been able to deliver the message to the recipient yet. Unfortunately, it has been delayed. We're working on delivering it. If you don't want to wait for the message sent to {Recipient} to finish being processed, you might want to ask the sender to send the message again using a different email address.
Contacting support won't solve this issue.
We haven't been able to deliver the message to the recipient yet due to a problem on your organization's email server. Validation ...
We haven't been able to deliver the message to the recipient yet. It looks like your remote server's firewall is blocking ...
We haven't been able to deliver the message to the recipient yet. Office 365 received an error because validation failed ...
We haven't been able to deliver the message to the recipient yet. This is either because we can't connect to the recipient ...
We haven't been able to deliver the message to the recipient yet. Unfortunately, it has been delayed. We're working on delivering ...
We haven't been able to deliver the message to the recipient yet. We can't deliver the message because Office 365 can't get ...
We haven't been able to deliver the message to the recipient yet. When we tried delivering the message, we couldn't connect ...
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 yet to the recipient because we can't connect to your organization's mail server. ...