To open MBOX files in Outlook PST format, you must convert the MBOX mailbox into a PST file because Outlook doesnt support MBOX directly. First, export or collect your MBOX files from your email client (Thunderbird, Apple Mail, Eudora, etc.). Then use a reliable MBOX to PST converter tool to scan, preview, and convert the data into PST format. After conversion, open Outlook and import the PST using File > Open & Export > Open Outlook Data File. All emails will load in Outlook folders.