I know this is an old post but I am hoping that someone will read and reply...
I am in exactly this situation, where importing using other methods are impractical because the user in question has over 3000 folders and subfolders and PST file is some 17GB in size.
My question is, how do you force Outlook 2007 to upload/sync all mail to the Exchange server?
Prior to now, mail was deleted off the server as it was received on the user's local machine, as he is by far the highest volume user in the office.
One of the reasons we're switching him to Entourage is that his giant PST file was slowing Outlook to a crawl and hopes are that Entourage with different file formats will not suffer as badly from his high-volume usage.