Exchange Online transport (mail flow) rules are a powerful way to manipulate messages as they pass through the transport system. In this example, we look at how to BCC messages sent by some employees for management review. I’m not sure that this is a good idea (for many reasons), but the need does exist to copy messages automatically, so we explore the use of transport rules as a solution.
You can configure Exchange Online distribution lists so that they reject messages sent to them as BCC recipients. I’m not sure how much use this feature will get, but it’s nice to have it anyway. PowerShell is the only management tool to configure distribution lists for the new block until Microsoft gets around to updating the Exchange Admin Center.