iCloud <=> mailbox
How to sync my iCloud items with my mailbox in Outlook?
The developers of the Apple iCloud AddIn do not work with the main Outlook calendar, but create a new iCloud calendar in a new Outlook data file. With the iCloud system control, the standard calendar can be transferred to the iCloud calendar once, but the automated merging is not possible for future appointments. So you have to enter all appointments in the iCloud calendar in the future. Since the appointment should usually also appear in the main calendar in order to remain compatible with other accessing programs, the entry would have to be made twice. Unfortunately, setting the iCloud Store as the default data file does not work either.
The solution: Use OLMixedFolders, which mirrors the appointments or contacts in the respective standard Outlook folders.
This configuration creates a new subfolder on your default mailbox calendar folder.