A common situation for IT departments is dealing with PST files left behind after employees move from desktop-based Outlook environments to Microsoft 365. These archives may contain years of communication that users still need for reference, audits, or customer history. When there are many users, simply importing each file individually can become difficult to coordinate.
Microsoft provides a Network Upload method for bringing PST files into Microsoft 365. The administrator can assign the required permissions, create an import job through Microsoft Purview, upload the PST files to Azure Storage using AzCopy, and then prepare a CSV file that maps each archive to its destination mailbox. After Microsoft validates the mapping information, the import can be started.
Before beginning the actual migration, I think it is worth reviewing the PST collection. An organization may discover that several employees have multiple archives containing overlapping information. Creating a list of files and their corresponding owners can help prevent confusion later. It also gives administrators a better idea of the total migration volume and which mailboxes should be processed first.
While looking at different ways of handling PST archives, I came across the DRS Softech PST File Converter. It includes a preview feature that allows users to examine mailbox folders and email information before processing. It also supports batch processing, selective data handling, attachment management, and folder hierarchy preservation. Those capabilities could be useful when an IT team needs to process archives belonging to many employees.
Another thing worth planning is how the migrated information will be organized. Users may already have folders such as Projects, Clients, Sent Items, or Department Archives. Maintaining the existing structure can make the historical data much easier to navigate after it reaches Microsoft 365.
For anyone planning to import Outlook PST to Office 365, I would also suggest running a pilot with a small number of representative archives. Afterward, administrators can check whether important folders, messages, attachments, and other supported mailbox items appear correctly in the destination accounts.
The choice between Microsoft’s native process and dedicated migration software will depend on the project. The native approach can work well for administrators comfortable with Microsoft 365, Purview, Azure, and CSV mapping. A specialized application may be more convenient when the project involves numerous PST files or requires additional data-selection and batch-processing controls.
