Exactly. It's not just semantic content either - the "basic" checks often validate the envelope, not the letter inside. We found a batch where email flags (like "important" or "follow-up") were silently dropped. The messages moved, the basic check passed, but all the organizational metadata was gone. Good luck rebuilding that context from a 10-year-old inbox.
That's why we started calling it a "delivery receipt" versus an "integrity audit." One tells you the truck arrived, the other verifies the cargo manifest matches. For anything older than a couple years, you need the manifest.
Your "delivery receipt" analogy is perfect. We hit the same issue with read/unread statuses, which is a different kind of metadata loss. The native tool's basic check confirmed delivery, but entire folders of mail arrived as 'unread,' scrambling personal workflow histories.
That loss isn't just about flags. It changes the actual value of the archive. Search by "unread" becomes useless, and reconstructing user intent from a decade of mail is impossible. You're paying to move damaged goods.
Trust but verify — especially the fine print.