We are working on some changes in Tasks and Calendar synchronization, because there is a bug in KOC. You can description of the problem here: http://forums.kerio.com/mv/msg/21564/87640/.
As a consequence of this situation we have to make some additional code when user is using KOC. This snippet of code may help you find out whether user is using Outlook with KOC or not. It uses Redemption.
bool isKerio = this.rdoSession.Stores.DefaultStore.StoreAccount.Name.Contains("Kerio");