Migrating MBOX file to Office 365 manually is difficult task to do it required many step to implement. Here are the manual steps to migrate MBOX to Office 365:

Step 1: Prepare MBOX Files
1. Export your emails into MBOX format.
2. In Thunderbird, install the ImportExportTools NG add-on if you need to export/import MBOX files.

Step 2: Move Emails from MBOX to Office 365 (via Thunderbird)
1. Install Microsoft Outlook on the same computer.
2. In Thunderbird, add your Office 365 account using IMAP.
3. Import your MBOX files into Thunderbird.
4. Select emails/folders from MBOX and drag-and-drop them into your Office 365 mailbox in Thunderbird.
5. Wait until all emails finish syncing to your Office 365 account.

Step 3: Import PST to Office 365 (Optional Backup)
1. Open Outlook (connected to Office 365).
2. Go to File → Open & Export → Import/Export.
3. Choose Import from another program or file → Outlook Data File (.pst).
4. Select the PST file and complete the import.

After applying these, you can move the MBOX file to Office 365. If these steps seem tough to apply, you can move your data with an automated tool called Shoviv MBOX to Office 365 Migrator. Using this tool, users can move the data in bulk while keeping data intact. The tool has many features and options that make everything selective and efficient for the users. Get the tool's free version installed and know all the features without buying the full version.

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