Final "talking to myself" reply (in case someone else will also need this): It turned out "Nokia PC Suite" (as opposed to "Nokia Suite") actually supports one-way "sync". You can choose whether to have a normal two-way sync, or whether it should go in Outlook>>N900 direction, or vice versa. As I hadn't changed anything on N900 beforehand, one-way Outlook>>N900 sync resolved everything. Also, the application will ask you, even in such one-way case, whether you want items (that are not in Outlook) to be deleted from N900. Great.