I recently needed to import multiple Outlook PST files into an Office 365 mailbox and found that there are a few reliable ways to do it--depending on the size of the PST files and whether you want a manual or automated approach. I'm sharing what worked best for me.

Manual Method (For Small PST Files)

If you have a small PST file, you can use Outlook's built-in import feature:

1. Open Outlook connected to your Office 365 account

2. Go to File → Open & Export → Import/Export

3. Choose Import from another program or file

4. Select Outlook Data File (.pst)

5. Browse the PST file and complete the import

This method works, but it can be slow and isn't ideal for large or multiple PST files.

Professional Method (Recommended)

For large PST files, multiple mailboxes, or to avoid errors, a professional tool is much easier. I used ATS PST to Office 365 Converter, which allows direct PST upload to Office 365 without Outlook dependency.

Benefits I noticed:

• Direct PST to Office 365 migration

• Supports large and multiple PST files

• Preserves folder structure, emails, and attachments

• Faster and more reliable than manual import

You just add the PST file, sign in to Office 365, and start the migration.

Manual import is fine for a one-time, small PST file. But if you're dealing with bulk migration or want a stress-free solution, using a professional PST to Office 365 tool like AyushTech PST Converter Software saves time and prevents data loss.

Hope this helps anyone looking for a smooth PST to Office 365 migration!