You’re right—there’s no direct native way to import MBOX into Office 365, so manual methods are often used.

Manual method: first import MBOX into Mozilla Thunderbird, then sync emails to Outlook using IMAP, or convert using an MBOX to PST converter and import the PST file into Outlook, then connect to Office 365. This process is lengthy and may affect data integrity.

A simpler option is RecoveryTools MBOX Converter to migrate to Office 365 , which allows direct migration with attachments, metadata, and folder structure intact. It also supports bulk transfer and advanced filters, making the process faster and more reliable.