The MFCMAPI utility is of great help to Microsoft 365 tenant administrators who want to understand the data apps store in Exchange Online mailboxes. An on-premises mailbox stores email data, but in the cloud, Microsoft 365 apps use Exchange Online as a convenient place to store data that needs to be accessible to services like Search and eDiscovery.
https://office365itpros.com/2023/10/27/mfcmapi-utility-primer/
