From Microsoft Corporation
MC218304, Stay Informed, Published date: Jul 11, 2020
Communication compliance now supports monitoring Team chat in an Exchange hybrid deployment where user’s primary mailbox is located on-premises. It will also automatically monitor all Teams that a user belongs to.
This message applies to tenants with one of these E5 or E3 licenses; otherwise, you can safely disregard this message.
When this will happen
These updates are available today.How this will affect your organization
You will no longer need to keep track of user Teams memberships.
What you need to do to prepare