If you want to open or access an Outlook PST file in an Office 365 account, the practical approach is to import the PST data into the Microsoft 365 mailbox. For larger PST files, manual methods can become time-consuming, especially when you need to preserve folders, attachments, contacts, calendars, or tasks. Softaken PST to Office 365 is designed for this type of migration. It supports PST and OST files, Office 365 destinations, folder hierarchy, attachments, contacts, calendars, and tasks. It also uses OAuth with Microsoft Graph for Office 365 authentication and provides pause/resume, duplicate protection, and HTML migration reports. A free trial is available to test the process first.

To open an Outlook PST file in an Office 365 account, you can use Outlook’s built-in import option or a dedicated MacSonik PST Viewer tool.

• Using Outlook: Open the desktop version of Outlook and sign in with your Microsoft 365 account. Go to File → Open & Export → Import/Export.
• Select Import from another program or file, choose Outlook Data File (.pst), and browse to your PST file.
• Select whether you want to import duplicate items and choose the folders you want to import.
• Select your Microsoft 365 mailbox as the destination and click Finish. Outlook will upload the PST contents into the selected Office 365 mailbox.

If Outlook is unavailable, the PST is orphaned/corrupted, or you need to migrate multiple large PST files, a third-party PST migration utility such as MacSonik can provide PST preview, filtering, folder preservation, and direct Microsoft 365 export options.

For enterprise migrations, administrators should also consider Microsoft 365 permissions, mailbox size limits, duplicate handling, and data integrity before starting the transfer. Always keep an original backup of the PST until the migration has been verified.

To open or access an Outlook PST file in an Office 365 account, you can use the Outlook Import/Export feature or Microsoft 365’s PST import process. For multiple PST files, use a professional MailsDaddy PST to Office 365 Migration Tool which is designed to directly migrate PST data to Office 365. 

The tool supports bulk and large PST files, selective folders migration, and provides a preview of the complete mailbox before starting migration. Also it preserves emails, attachments, folder structure, and other mailbox items throughout the process without any hassle. This is particularly useful for bulk migration when manually importing each PST file would be time-consuming.