Import PST file to Office 365 for multiple mailboxes requires proper handling of mailbox mapping, folder structure, and Outlook data. PST files can contain emails, contacts, calendars, tasks, attachments, and other mailbox items that need to be transferred accurately. Managing multiple PST files manually can become time-consuming, particularly when dealing with large files, duplicate items, or different user mailboxes. The Cigati PST to Office 365 Migration Tool provides an option to migrate PST data to Office 365 mailboxes while maintaining the folder hierarchy and supporting selective data transfer. It can be useful for organizations handling multiple PST files during Microsoft 365 migration.
here is only single solution to directly Import Outlook PST files to Office 365 server with complete mailbox items. Using KDETools PST to Office 365 Converter tool capable to Migrate multiple PST files to Office 365 accounts with all mailbox folders, sub-folders, contacts, calendar etc.
When you have multiple PST files and multiple Office 365 mailboxes, the main challenge is mapping each PST to the correct Microsoft 365 account without mixing mailbox data. A practical approach is to process the PST files in batches, select the required folders and authenticate each destination mailbox through OAuth 2.0 and Microsoft Graph API. I would look at Softaken PST & OST to Office 365 / IMAP Importer for this setup because it supports batch PST processing, folder hierarchy, attachments, contacts, calendars and tasks. You can also use duplicate protection, pause/resume and retry failed items when needed. Before starting the full migration, test a few PST to mailbox mappings first and confirm that each archive is landing in the intended Office 365 account.
To add PST files to multiple Office 365 mailboxes, users must first configure all Office 365 accounts in Outlook one by one. Subsequently, they have to manually import the PST files into the respective accounts by navigating to File > Open & Export > Import/Export. While this method works well for a small number of accounts, it carries risks—such as metadata loss, PST corruption, or importing a PST file into the wrong mailbox—when dealing with a large number of PST files. To avoid these issues, users can utilize BitRecover PST to Office 365 Migration Tool, which allows multiple PST files to be transferred directly to their correct Office 365 mailboxes without the need for account configuration or individual imports.