When sending outbound through Email Security .cloud, an email sent to one or more recipients outside your organization fails to arrive to the intended recipients.
- No Non Delivery Report (NDR)
- Within the Client portal, Email Track and Trace does not show a delivery attempt to the target recipient
The ReturnPath/Envelope Sender of the email for the DL is a Null Sender by default in Office 365. The "Sender" in your Office 365 report is simply a "Body From" and is not the SMTP sending address. As a result Symantec .cloud servers cannot verify that the email is legitimately from a customer, so they respond with a "trying to use me as a relay" message.
Within Office 365, on the settings for the DL, set a manager for the DL that is an address within a domain protected by Email delivery . cloud
Using a Powershell command enter "set -ReportToManagerEnabled $true"