I see duplicate contacts when I switched to CardDAV protocol

Summary

Kerio Sync Connector synchronized contacts to a different local AddressBook storage than CardDAV protocol do. It can cause that AddressBook returns multiple contacts, each from a different local storage. One which has been localy stored by Kerio Sync Connector previously, the other which is being synchronized by CardDAV account. You can delete locally based contact previously synced by Kerio Sync Connector. It is very important that Kerio Sync Connector must be uninstalled before you delete local address book entry. Otherwise this change can be synchronized back to the Kerio Connect server and contact will be lost.

Details

Transition from Kerio Sync Connector to a CardDAV account

1. Uninstall Kerio Sync Connector from your MacOS X 10.6. machine
2. Navigate to "Integration with MacOS X" page in webmail settings
3. Download and run autoconfiguration tool for AddressBook based in the integration page
4. Resolve possible duplicates by deleting contact which is locally stored, not the one from the new CardDAV account.