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 only when the device was not used for an extended period of time ( more than 1 month) or if there was some server migration that lost the data.
In those cases, repairing the account or removing or re-adding it should resolve it, as full resynchronization should fix any inconsistencies in the data - but in the current reported cases, the same error keeps returning.
Our devs will be adding some code to eM Client to resync the account automatically when this error shows up, but since we could not completely replicate the behavior on our side, creating a fix has become more difficult than usual. We’re sorry for the inconvenience.
If you have a test account or less used account where this issue can be replicated that you’d be willing to provide temporarily for testing, please send the details to [email protected].
It would greatly help us in troubleshooting and finding the workaround to this issue.
If you do not need to synchronize the Calendar and Contacts for this account, and would prefer to just stop the errors for now you can turn off AirSync service for the account - this can be problematic for those who use AirSync to SEND emails via the outlook account (which is a change we made previously due to OAuth issues on Microsoft servers).
So to be able to keep sending from the outlook account, you need to set eM Client to use SMTP for sending emails for outlook.com accounts:
- In Registry location Computer\HKEY_CURRENT_USER\Software\eM Client a DWORD value needs to be added - UseAirSyncSendMail set to 0 (you can either do this manually or run this file: UseAirSyncSendMail0.reg)
- Then restart eM Client - it will now use SMTP to send messages and you can turn off the AirSync service in General tab in Menu>Accounts for the affected account.