Check the email addresses, subject line, and date, and run the checks again. If that doesn't work, contact the sender and ...

Office 365

Check the email addresses, subject line, and date, and run the checks again.

If that doesn't work, contact the sender and ask if they received an email that explains why the message wasn't delivered (non-delivery report). The problem seems to be happening before the message arrives at the Office 365 mail servers. You might want to verify that your organization's mail servers have been correctly set up to send mail to Office 365. Follow these steps:Go to the connectors page.
Choose the Check to see if you should create a connector link in the first paragraph, and follow the step-by-step instructions.

Check the box next to each account you want to remove. Once the account is removed, the external user won't be able to access ... Check the email address, and run the checks again. If you entered the correct email address, you need to either create a ... Check the email address, and run the checks again. If you entered the correct email address, you need to either create a ... Check the email addresses, subject line, and date, and run the checks again. If that doesn't work, contact the sender and ... Check the email addresses, subject line, and date, and run the checks again. If that doesn't work, contact the sender and ... Check the email addresses, subject line, and date, and run the checks again. If that doesn't work, contact the sender and ... Check the email addresses, subject line, and date, and then click Back to run the checks again. If that doesn't work, contact ... Check the Message Events table below for any additional information about why message delivery might be delayed. For example, ... Check the Service health dashboard to make sure that there isn't a service outage affecting your organization. If there's ...