How to Migrate Outlook PST to Office 365?

If you’re switching to Office 365 or Microsoft 365, you also have to migrate the mailboxes and other items from the current on-premises environment to Microsoft 365. This can be done by importing or migrating Outlook PST files containing the emails, contacts, attachments, etc., to Microsoft 365 mailboxes.

In this article, we have shared different ways that can help you to quickly migrate Outlook PST files to Microsoft 365 while maintaining the original mail folder and items structure.

Methods to Migrate Outlook PST Files to Office 365

There are four different ways to migrate Outlook PST files to Microsoft 365. Depending on the number of Outlook PST files you need to upload or migrate to  Microsoft 365, you may choose any of the following methods:

  • Import Outlook PST via Outlook Import Export Wizard

Use this method when you need to migrate a few small Outlook PST files to Office 365.

  • Network Upload using AzureAZCopy Tool

The method is useful when you need to import large or multiple PST files into Microsoft 365. You can import PST files up to 20 GB to avoid performance issues.

  • Ship the Drive Containing PST Files to Microsoft

You can send or ship your large PST files in an encrypted hard drive to Microsoft and pay them to upload PST files to your Azure Storage for import. The method is recommended when there is a network or bandwidth-related issue.

A specialized PST migration software helps you directly migrate Outlook PST files up to 50 GB to Microsoft 365 in a few clicks, with complete integrity and consistency. It helps you move PST or OST files from multiple systems directly to  Microsoft 365 mailboxes.

Method 1: Use Outlook Import Export Wizard

To import Outlook PST into Office 365 via Import/Export wizard, follow these steps:

  • Sign in or add your Microsoft 365 email account to the Outlook client.
  • After adding the account, go to File > Open & Export and click Import/Export.
  • Select Import from another program or file and click Next.
  • Select Outlook Data File (.pst) and click Next.
  • Click Browse to choose the PST file and click Next.
  • Choose the  Microsoft 365 email account and click Finish.


import outlook pst data file

  • After the import, you can access the mail items from your Microsoft 365 mailbox.

Repeat these steps to import PST files into other  Microsoft 365 accounts.

Method 2: Network Upload using AzureAZCopy Tool

To use the method, you must assign the Import Export and Mail Recipients roles to the user account you will be using to upload the Outlook PST to Office 365. You will also require the AzureAZCopy tool.

The steps are as follows:

Step 1: Assign Roles

  • Log in to the Exchange Admin Center and click Roles > Admin Roles. Next, search and click ‘import export.’

assign import export role to the user

  • Click Add under the Assigned tab and choose the user you want to assign the role for importing the Outlook PST file.

choose user to assign import export role

  • Search and select users and click Add.

users with import export role assigned

Step 2: Create an Import Job

To create an Outlook PST to Office 365 import job for uploading PST files to Azure Storage, follow these steps:

  • Visit homepage and click Data lifecycle management > Import.
  • Click Import PST Files.

select import pst files option

  • Click + New import job and then enter the job name.
  • Click Next and then select Upload your data in SelectImport Job Type > Next.

select upload your data option

  • Click Show network upload SAS URL.
  • Next, click Copy to clipboard and then click Download Azure AzCopy to download the tool. The Azure AzCopy tool is available for Windows, Linux, and macOS.

copy sas url download azure azcopy tool

Note: Do not close this until the PST files are uploaded to Azure Storage.

Step 3: Upload PST Files to Azure Storage

To start uploading the Outlook PST files to Office 365 Azure Storage, follow these steps:

  • After download, extract the tool on the Desktop and copy the folder containing the PST files on the Desktop or connect the drive if stored on the external media.
  • Open Command Prompt and navigate to the extracted folder on the Desktop where the azcopy.exe file is located using the ‘cd’ command.
  • Then run the following command to upload the PST files to Azure Storage.

Azcopy copy “pathToFolder/ContainingPST” “SAS URL” --recursive=true

upload folder containing pst files to azure storage

Wait for the PST files to upload. This may take a while, depending on your network speed and bandwidth.

Note: Ensure that PST files do not exceed the 20 GB recommended limit as they can impact and degrade the import process.

Step 4: Verify Uploaded Outlook PST Files

To verify that the PST files are uploaded successfully on the Azure Storage, you can use the Azure Storage Explorer. The tool is available for Windows, macOS, and Linux. Follow these steps:

  • After the download, launch the installer and click ‘Install for me only.’
  • Complete the installation and then launch the Azure Storage Explorer.
  • Select Blob container > Shared access signature URL (SAS) and paste the SAS URL you had copied in the Blob container SAS URL: field.

upload pst office365 verify pst uploads

  • Click Next > Connect.
  • Under File Shares, you can see the PST folder. Open it to check PST files are there.

check verify all pst files in azure storage

Step 5: Map Outlook PST Files

The next step is to map the PST files with the user mailboxes. This is critical as you need to ensure PSTs are correctly imported into user mailboxes on Microsoft 365. For this, you can use this sample PstImportMappingFile.csv.


map pst files with office 365 mailbox csv file

Leave the Workload, enter the FilePath (folder name), Name, Mailbox, and TargetRootFolder where mail items will be imported. You may leave other fields empty. Save the .CSV file.

Step 6: Start PST Import Job

To start the PST import, go back to the Microsoft 365 Import data wizard and follow these steps:

  • Tick on I’m done uploading my files and I have access to the mapping file check boxes and click Next.

complete the steps to upload import pst files to office 365

  • Click +Select mapping file and then click Validate. Once validated, click Next. If validation fails, download the logs and check the issue.


upload csv pst mapping file

  • Click Submit and then click Done.

complete the steps to upload import pst files to office 365

check the import progress

  • Once imported, the message will change to Import completed.

pst import to office 365 via upload method complete

  • You may also log in to your Microsoft 365 account where PST is imported and check the folder and mail items.

Users should now have access to all their mail items.

Method 3: Ship the Drive Containing PST Files to Microsoft

You may also send or ship your Outlook PST files to Microsoft and ask them to upload them to your Azure Storage. You can use Command Prompt to run Azure Import/Export tool, which transfers the PST files, create a journal file (abc.jrn), and encrypt the hard drive with BitLocker.

Microsoft charges $2/1GB or $2000/1TB of PST files. Once the PSTs are uploaded, create an import job, and this time, choose Ship hard drives to one of our physical locations. Refer to this Microsoft document for complete steps.

Ensure each PST file you add to the hard drive is not larger than 20 GB as it can impact the PST import performance.

Method 4: Outlook PST to Office 365 Migration Tool

With an Outlook PST to Office 365 migration tool, such as Stellar Migrator for Outlook, you can select, scan, and upload PST files directly to Microsoft 365. The software securely connects to the mailbox using the Microsoft Modern Authentication and starts uploading the mail items from the selected Outlook PST file to your Microsoft 365 mailbox.

The software keeps the original folder structure and hierarchy intact. If not found in the mailbox, it creates mail folders and migrates the mail items. It also merges the mail items in existing folders, such as Inbox, Sent Items, etc. to avoid duplicate mail folders.

You can install the software on multiple systems to simultaneously upload several large PST files up to 50 GB each to Office 365. You may also upload and migrate mail items from Outlook OST files, including orphaned or inaccessible OST files, to Microsoft 365 files. Most importantly, you only have to ‘pay per mailbox’ upload, irrespective of the PST file size.


Migrating PST to Office 365 manually is a cumbersome and tedious job that requires you to perform multiple steps. In addition, there’s no GUI to interact with when you upload the PSTs to Microsoft 365 Azure Storage. Only after the import, you can verify if all mail items and folders are imported successfully or not. Thus, it’s recommended to use a specialized PST migration tool to upload and migrate PST files to Office 365. In addition, the GUI-based software allows you to add filters to include/exclude Junk/Deleted Items and choose only mail items or folders you want to migrate to Microsoft 365.

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Ravi Singh linkdin Icon

Senior Writer at Stellar®. He is an expert Tech Explainer.

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