How can I also synchronize my archive folder and what do I have to observe?

If you already synchronize both your "Personal Folders" and your "Archive Folders", you will need either the Business Edition or the Manager Edition. These editions allow for multiple users to create Outlook Groups, thus allowing for multiple Outlook data files.

Important note: If you use the auto-archive feature of Outlook, then you need only to activate it on a single computer. This computer then automatically synchronizes your Outlook items from both the personal folder and the archive folder. Both data files are then synchronized and archived virtually on all other computers.