One of our clients migrated their mailboxes from on-premises to EXO using a 3rd party tool as part of the staged migration process (the cut-over is not done yet as they're gradually doing pre-seed batch by batch). It all went well and after a few weeks, they noticed a significant decrease in the migrated mailbox items volume across all mailboxes which appears to be a purge and they have no clue of how/when it occurred.
Here's a sample mailbox. If they do a content search, the result returns with reasonable volume of content but the number doesn't match with the actual EXO mailbox.
Content search result: It should be more than 2GB
Actual Mailbox status:
Online archive is enabled but nothing has moved there anyway. We've checked the audit logs and found nothing relevant towards purge or move.
Any idea what's going on here?
