Entourage mail creates MBOX files for archive data. But MS Outlook does not support MBOX extension which requires MBOX to PST conversion. You can use QuickData MBOX to PST Converter to export Entourage mail archives to Outlook PST format.
One can convert .mbox files to PST file which is accepted by MAC as well as Windows Outlook editions. To do the conversion, a reliable software is required. You cab use QuickData MBOX to PST Converter which is available free of cost for trial purpose.