This is an interesting case that I recently worked on and would like to share as part of this series. An organization that uses Exchange Online Protection was receiving automated emails from a partner. These emails were arriving with empty subjects and bodies. When the partner sent the automated emails to a Hotmail.com / outlook.com address, they would also arrive with no subject or body. However, when the partner sent these emails to a Gmail account, the would arrive just fine with the subject and body intact.
In this article I walk through how I troubleshot this problem and what the final root cause was.
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