You can import PST files to Office 365 (Microsoft 365) either for an individual mailbox using the classic Outlook desktop client or in bulk for your entire organization using the official Network Upload method via the Microsoft Purview Portal.
Method 1: For Individual Users (Using Classic Outlook)

1. Open the classic Outlook desktop app configured with your Office 365 account.
2. Click File > Open & Export > Import/Export.
3. Select Import from another program or file, then click Next.
4. Choose Outlook Data File (.pst) and click Next.
5. Browse and select your .pst file, choose how to handle duplicates, and click Next.
6. Select your Office 365 mailbox as the destination and click Finish.

For users looking for an easier alternative to Microsoft's complex network upload or the manual Outlook method, a specialized utility like Recoveryfix Import PST to Office 365  can streamline the entire process.
Why Choose Recoveryfix Import PST to Office 365?

Direct Cloud Migration: It securely uploads local Outlook .pst files directly into Office 365 (Microsoft 365) cloud mailboxes without complex command-line scripts or Azure storage setups.
Bulk Import Capabilities: Administrators can map and import multiple PST files into multiple user mailboxes simultaneously using a simple CSV file.
Smart Data Filtering: The software allows you to filter emails by date range or specific folder types so you only upload relevant data.
Maintains Folder Hierarchy: It preserves the exact original structure of your folders, subfolders, read/unread status, and email metadata during transmission.