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In some use-cases, you might want to export Office 365 mailboxes to a PST file. For example when a user leaves the organization, legal purposes, or when you want to migrate a mailbox to another mail service.

Users can export their own mailbox through the Outlook client, but also as an admin we can easily export a complete mailbox through the Office 365 Admin Center.

In this article, I am going to explain how you can export an Office 365 mailbox to pst.

Requirements to Export Mailbox to PST in Office 365

We are going to use the Content Search and eDiscovery Export Tool to export an Office 365 mailbox to PST. To use the Content Search you will need to have the eDiscovery Manager role in the Microsoft 365 Compliance center.

A global administrator doesn’t have this role by default, so first, we are going to give your account the proper permissions. You will need to be a global administrator to change permissions.

  1. Log in at the Microsoft 365 Admin Center
  2. In the menu, click on Compliance to open the Compliance Admin Center.
  3. Click on Permissions
  4. And open the Compliance Center Roles
  1. Select eDiscovery Manager
  2. Make sure that the Export Role is listed in the Assigned Roles (otherwise add it)
  3. Edit the eDiscovery Administrator
  1. Click on Choose eDisovery Administrator or Edit
  2. Click + Add
  3. Lookup your own account and add it to the list
  4. Clic Save to complete

We have now the proper permissions to start a Content Search and export an Office 365 mailbox to pst. To apply the new permissions it’s best to log out, close the tab and log back in again.

Office 365 Export Mailbox to PST

To export a mailbox out of Office 365 we first need to create a Content Search that will collect all the mail of the specified user. Then we can export the result to a PST file with the eDiscovery Export Tool.

Note: Only the browser Edge is supported to download the eDiscovery Export Tool.

Their are browser extensions available for Chrome and Firefox that solve this issue and allows you to download and use the eDiscovery Export Tool

Chome : Meta4 ClickOnce
Firefox : Breez ClickOnce

  1. Open the Microsoft 365 Compliance Center
  2. Create a new Content Search
    – Select Content Search in the menu under Solutions
    – Click + New Search

3. Enter a name and description

Give your content search a recognizable name and description and click Next. This helps you later with identifying the correct content search.

4. Select Exchange Mailboxes

To export a mailbox, turn Exchange Mailboxes on and click on Choose users, groups, or Teams

5. Select the mailbox to Export

The next step is to select the mailbox that we want to export. Select or search the correct user and click on Done

And click on Next to continue to the Conditions.

6. Leave Conditions empty

We want to export the complete mailbox, so we can leave the conditions empty.
Just click Next

7. Complete the Content Search

Review your Content Search and click Submit to start it.
Click Done to close the New Search screen

8. Wait for the search to complete

Depending on the mailbox size it can take a couple of minutes to complete the content search. Wait for the status to change to Completed in the Content Search scene. (Click Refresh occasionally to update the status)

9. Export the Office 365 Mailbox to PST

1. Click on the Content Search that we have just created
2. Select Actions
3. Choose Export results

10. Export Options

We can now select what and how we want to export our mailbox.
– Output Options: All items, including ones that have unrecognized format…
– Export Exchange Content as: One PST file for each Mailbox.

Click Export to start the export

11. Download the Office 365 export mailbox PST file

Again, it can take a couple of minutes for the download file to get ready.

– Open the Export tab in the content search screen
– Select the Export job to view the status

12. Download eDiscovery Export Tool

To download the PST files we will need to use the eDiscovery Export Tool.
As mentioned earlier in the blue note, you will need to use Edge for this step or use a ClickOnce browser extension in Chrome or Firefox.

Click Download Results to download the tool

13. Approve the download

A new tab will open that will download the eDiscovery Tool. Click Open in the security warning

14. Copy the Export Key

Before you can start the download, you will need to copy the export key from the Compliance Center.

15. Download the PST File

The last step is to start the download in the eDiscovery Export Tool.

1. Paste the key that we copied
2. Enter a location for the PST file
3. Expand Advanced Options and give the PST file a meaningful name

And click on Start

16. Wait for the download to finish

Depending on the size of the mailbox, the download can take some time. Wait for it to
finish and open the PST file in the location that you specified.

You can also use these steps to download multiple mailboxes at once. Just select multiple users or mailboxes at step 5 and makes sure that you select one pst file for each mailbox in step 10.

Office 365 Export PST File Size Limit

The default file size of the exported PST files is 10 GB. You can increase or decrease the file size, but keep in mind that if you make it too large, to change of file corruption increases as well.

Making the file size smaller can be useful if you need to place the files on removable media.

To change the file size you will need to create a registry key.

  1. Close the eDiscovery Export Tool
  2. Create a new txt file and name it pstsize.reg (note the extention)
  3. Add the following content
1. Windows Registry Editor Version 5.00
2. [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Exchange\Client\eDiscovery\ExportTool]
3. "PstSizeLimitInBytes"="21474836480"

4. Change the PstSizeLimitInBytes to the desired value:

Size in bytesSize in GB
42949672964 GB
85899345928 GB
2147483648020 GB
3221225472030 GB
  1. Save the file and close it.
  2. Double-click the newly created reg file to import it. Click yes twice to the warnings.

You can remove the registry key to change the value back to 10 GB or change the value of the key to 10737418240.

Restart the eDiscovery tool to export the PST files in the new size.

Export or Backup Office Outlook contacts

When users leave the organization they sometimes want to take their Outlook contacts with them. Even though you can easily export them through Outlook, you could also use the Content Search method to export only the contacts.

Follow all the steps described earlier, but add a condition in Step 6:

  1. Click Add Condition
  2. Select Type
  3. Click Add/Remove more options
  4. Select Contacts

Follow all the other steps to export the Outlook contact to a PST file.

Use a third-party tool to Export Mailbox to PST

There are also third-party tools available to export Office 365 mailboxes to PST files. For example, Kernel Export Office 365 to PST Tool (10% discount with code “lazyadmin”), SysTools Backup and Restore Office 365, or Stellar Exporter for Office 365. Now I am not going to do a full review of these tools, but what is great about these kinds of tools is that they give you more control and feedback about the export.

For a single mailbox is this overkill, but if you have to export multiple mailboxes, or do this on a more regular basis, then this tool is a real-time-saver. It makes exporting Office 365 mailboxes to PST a lot easier.

Wrapping Up

I hope this article helped you with your Office 365 Export mailbox to PST. Keep in mind that the content search method can take some time. If you need to export multiple mailboxes to PST then using a third-party tool might be a better idea.

They are more convenient to use and don’t cost really that much.

If you have any questions, just drop a comment below.