Hi @Rising Flight
Resource mailboxes, contacts, and Microsoft 365 group mailboxes aren't supported for Exchange email. For Microsoft 365 group mailboxes, select the Microsoft 365 Groups location instead. Although the Exchange location initially allows a group mailbox to be selected for a static scope, when you try to save the retention policy, you receive an error that "RemoteGroupMailbox" is not a valid selection for this location.
For more information, you could refer to:
https://learn.microsoft.com/en-us/microsoft-365/compliance/retention-settings?view=o365-worldwide#configuration-information-for-exchange-email-and-exchange-public-folders
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