Cause

The issue is caused when the mailbox quota for user is reached in Exchange Online.

Traceback

[ERROR] Could not list MAPI folder Inbox:AQMkAGRhNmJiAGViOS1hZTlkLTQ1M2QtYWRmOS03OTkBZThlYjQyNzkALgAAA1PuA5wAFNFCvLm9jLeb6O0BAJeA1BnmM4-BU6wAAAIBDAAAAA==. Cloudapp Skipping. type:MAPI Email Error:Unable to read file. Permission Denied Response Code: 403 Text:{"error":{"code":"ErrorQuotaExceeded","message":"The process failed to get the correct properties."}} (#100000046)

See also

https://docs.druva.com/SaaS_Apps/Protect_Microsoft_365_Apps/020_Protect_Exchange_Online/080_Troubleshoot_Exchange_Online_issues