FolderHierarchyChanged error when syncing a hotmail account

[Gary]

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Outlook error [AirSync] Synchronization error (SyncStateNotFound)

Recently, we have seen a lot of reports of Outlook calendar issues, the error usually looks like this: [AirSync] Synchronization error (SyncStateNotFound) In the log the error can also include details like Found invalid data while decoding. and Folder hierarchy changed. We are aware of this error but unfortunately had no luck replicating it yet or finding the real cause yet. The error usually means the server lost sync data for a particular device and account. That should normally happen o…