PST file won't open—how can I recover my emails?

I would not convert the PST files to PDF before importing them. PDF is useful for reading or archiving messages, but it cannot preserve a working Outlook mailbox structure the way a PST can.

First, try opening and repairing a copy of each PST with classic Outlook:

1. Make a backup copy of the PST and keep the original untouched.
2. In classic Outlook, open File > Open & Export > Open Outlook Data File.
3. If it will not open, close Outlook and run Microsoft’s Inbox Repair Tool, SCANPST.EXE.
4. Select the copied PST, run the scan, enable the backup option and repair the file.
5. Reopen the repaired copy in Outlook. A badly damaged PST may need more than one scan.

Once it opens, import it into your Microsoft 365 mailbox:

1. Open File > Open & Export > Import/Export.
2. Select Import from another program or file.
3. Choose Outlook Data File (.pst).
4. Select the PST and its top-level folder.
5. Enable Include subfolders and import it into your Microsoft 365 mailbox.

This should preserve the Outlook folders, messages and attachments. Check the mailbox storage limit first. For several very large PST files, ask the Microsoft 365 administrator to use the Microsoft 365 PST Import service instead of importing everything through Outlook.

For PDF copies, classic Outlook can print individual messages through Microsoft Print to PDF, but attachments and folder structure are not preserved automatically. For bulk PDF archiving, Adobe Acrobat Pro’s Outlook integration is a paid option that can convert selected messages or folders and create a PDF Portfolio containing attachments. Repair and open the PST in Outlook before using it.

Avoid uploading work PST files to an unknown online converter because they can contain years of private messages and attachments.