You can import an archived Outlook file into your new Office 365 Inbox. It is easy and you will find that all your mail messages from the old system can be imported with just a few clicks. This article assumes you already have an Outlook export in the form of a .pst file.
If you are experiencing problems importing your .pst file after following the below directions, please submit a support case here explaining the issue and someone will get to you as soon as possible to get it resolved.
1. Log into the Outlook application on your computer
2. Click on the File tab and then click on the Open & Export button from the left side of the screen.
3. Click on Import/Export.
4. This will open Import and Export Wizard.
5. Select Import from another program or file
6. Click Next.
7. Select Outlook Data File (.pst).
8. Click Next.
9. Click Browse... to select your .pst file.
10. Click Next.
11. Leave the default settings intact and click Finish.
At the bottom of the screen, just above the task bar, you will see “Updating (folder name). This folder is up to date." run across the bar. The message changes for every folder that is in the process of importing. When the job of importing your .pst file is complete you see “All folders are up to date”. To verify this, you can click on the arrow next to the Inbox folder and see all your folders and messages incorporated into your Office 365 inbox.
Even after importing a large .pst file you will have plenty of space in the new system. Every IPSD email user now has a 100 GB mail box.