NDR - Office 365: Your message did not reach some or all of the intended recipients.

Or, the following recipient(s) cannot be reached, Outlook 2013 (Office 365 Server).

Problem Description:

This is a known behavior and it happens rarely due to common issues like wireless connectivity hangs, if outlook did not respond well when you click on send button etc.

The possible reason for the error you are facing could be the user was having some intermittent networking issue that happened to hit at the time the message was submitted. This behavior occurs because of a busy or unreachable Internet Mail server when you connect through your Internet service provider (ISP).

This behavior is by design and the error is expected when network failures occur.

In general, this problem is likely caused by intermittent network connectivity issues, or possibly out-of-resource problem on the client machine. Also refer this link MS reference KB : https://support.microsoft.com/en-us/kb/286106

NDR/Error Screenshot:

Solution:

Re-sending this type of email (Using Send Again button) is the available work around for this issue.

Timely windows update and reboot, up to date drivers etc. can help you in getting rid of such issues if it’s occurrence is very frequent for few of the users.