Microsoft 365 Export Mailbox to PST

Feb - 07 2023 | By

If you want to export the contents of a user in Microsoft 365 to a Outlook PST file follow these steps.  These all should be done using Microsoft Edge.  Microsoft Edge is the only one that seems to work with the export download.

Check that your username at Microsoft 365 can Export

  • Sign in at
  • Click Permissions from the menu on the left
  • Choose Microsoft Purview Solutions, Roles
  • Choose eDiscovery Manager
  • From Assigned roles, make sure Export is listed and that your username is listed here if not click Edit and add Export and choose your username to eDiscovery Administrator, then click Save.

Export Steps

Now that the username has the ability to export content we can go through the steps.

  1. Make sure your signed in at
  2. Choose Content search on the left menu.
  3. Choose New search from the menu at the top, under the Search tab.
  4. Provide a Name and description for the search – like Export Mailbox John Doe, click Next.
  5. In the Locations page turn on Status column for Exchange mailboxes, then click Choose users, groups or teams, type in the email address of the user you want to Export to a PST file, check their name click Done.  Then click Next.
  6. In the Define your search conditions, just click Next.
  7. On Review your search and create it, click Submit.
  8. On the Content Search page wait for it to show Completed, you can click the Refresh button at the top to update the status.
  9. When complete, click your Export at the bottom left under Actions menu choose Export results.
  10. On Export results, choose All items, including ones that have unrecognized format, are encrypted, or weren’t index for other reasons and choose One PST file for each mailbox. Then click Export.
  11. Go to the Export tab and watch the progress of your Export, you can click Refresh at the top to update the status.
  12. When completed click the Export for the Mailbox copy the Export key that is required to download your PST file.
  13. After copying the Export key click Download results at the top of the Window.
  14. It will ask you about opening a file, Microsoft.Office.Client.Discovery.UnifiedExportTool.application, choose Open
    Agree to allow the application to Run.
  15. It will ask for the Export key in the first box, paste the Export Key you just copied, click Browse to choose where to save the files, and from Advanced options I recommend choosing a name for the file otherwise it just names it export.pst.
  16. Wait for the download to finish and wait for the Close dialog then you will find a folder in the location you choose to save your export with all the information from the export.

Microsoft 365 Export PST File Size Limit

Microsoft has the default size of the exported PST files to 10GB, you can increase or decrease the file size.  Larger PST files are more likely to become corrupted.

You can create a registry import file with the following

Windows Registry Editor Version 5.00

Double click the newly created Reg file you have just created and agree to import the Registry change.

Where the PstSizeLimitInBytes can be 4294967296 – 4GB or 8589934592 – 8GB or 10737418240 – 10GB or 2147436480 – 20GB or 32212254720 – 30GB.  The restart the eDiscovery download to export PST files in the new size.

After you are finished you should restore this PstSizeLimitInBytes back to the default setting you had.