How to Migrate PST Files to Microsoft 365: Complete Step-by-Step Guide
4 methods explained with full step-by-step instructions. From the simple Outlook import wizard to enterprise-scale network upload — choose the right method for your data volume.
PST files are the silent data problem in most email migrations. While everyone focuses on migrating live mailboxes, the average user has 3.2GB of PST archive data sitting on their local computer — containing years of emails, contracts, and customer history that never makes it to the new platform.
This guide covers all four methods for importing PST files to Microsoft 365, with complete step-by-step instructions for each. We also cover troubleshooting common errors and how to verify the import was successful.
Which Method Should You Use?
Under 10GB
Outlook Import Wizard
10GB – 1TB
Network Upload (Compliance Center)
1TB+
Drive Shipping
Any size (enterprise)
Third-Party Migration Tool
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All 4 PST Import Methods: Step-by-Step
Outlook Import Wizard
Best for: Small volumes (under 10GB), individual users
Step-by-Step Instructions
- 1Open Outlook on your desktop
- 2Click File > Open & Export > Import/Export
- 3Select "Import from another program or file"
- 4Choose "Outlook Data File (.pst)"
- 5Browse to your PST file location
- 6Select import options (replace duplicates, allow duplicates, or do not import duplicates)
- 7Choose the destination folder (or import to top-level folder)
- 8Click Finish and wait for import to complete
Pros
- No admin access required
- Simple and familiar interface
- Works for any user
Cons
- Slow for large files
- Must be done on each computer individually
- Outlook must be open during import
Microsoft 365 Network Upload (Compliance Center)
Best for: Medium to large volumes (10GB–1TB), bulk imports
Step-by-Step Instructions
- 1Sign in to Microsoft Purview Compliance portal (compliance.microsoft.com)
- 2Go to Data lifecycle management > Import > Import PST files
- 3Click "New import job" and name it
- 4Select "Upload your data" (network upload)
- 5Download and install the Azure AzCopy tool
- 6Copy the SAS URL from the import job
- 7Use AzCopy to upload PST files: AzCopy.exe copy "C:\PSTs" "[SAS URL]" --recursive
- 8Create a CSV mapping file specifying which PST goes to which mailbox
- 9Upload the CSV mapping file in the Compliance portal
- 10Review and start the import job
- 11Monitor progress in the import job dashboard
Pros
- Handles large volumes efficiently
- Bulk import to multiple mailboxes
- No physical media required
Cons
- Requires admin access
- Technical setup with AzCopy
- Upload speed limited by internet connection
Drive Shipping (Mail Hard Drive to Microsoft)
Best for: Very large volumes (1TB+) or slow internet connections
Step-by-Step Instructions
- 1Create an import job in Microsoft Purview Compliance portal
- 2Select "Ship your data" option
- 3Download the WAImportExport tool from Microsoft
- 4Copy PST files to a hard drive using the WAImportExport tool (encrypts with BitLocker)
- 5Create a journal file documenting the drive contents
- 6Ship the hard drive to the Microsoft data center address provided
- 7Enter the tracking number in the import job
- 8Create and upload the CSV mapping file
- 9Microsoft uploads the data (7–10 business days)
- 10Review and complete the import job
Pros
- Best for very large data volumes
- Not limited by internet speed
- Secure BitLocker encryption
Cons
- Slowest method overall
- Shipping costs and logistics
- Hard drive is not returned
Third-Party Migration Tools
Best for: Enterprise migrations, complex scenarios, automated bulk imports
Step-by-Step Instructions
- 1Choose a tool: BitTitan MigrationWiz, SkyKick, CodeTwo, or Stellar Converter
- 2Create a migration project in the tool
- 3Connect to your Microsoft 365 tenant (OAuth or admin credentials)
- 4Upload PST files to the tool's staging area or point to a network share
- 5Map PST files to destination mailboxes using the tool's interface
- 6Run a pre-migration analysis to check for issues
- 7Start the migration (tool handles upload, mapping, and error handling)
- 8Review migration report and re-run failed items
- 9Verify imported emails in Outlook
Pros
- Automated error handling and retry
- Parallel processing for speed
- Detailed migration reports
- No technical expertise required
Cons
- Licensing cost ($10–$30 per mailbox)
- Requires third-party account setup
Common PST Import Errors and Fixes
Error: PST file is too large (over 20GB)
Fix: Split the PST file using SplitPST or Stellar Splitter before importing. Keep individual files under 20GB for reliable imports.
Import job stuck at "In progress" for more than 24 hours
Fix: Check the AzCopy upload completed successfully. Verify the CSV mapping file has no formatting errors. Check that the SAS URL has not expired (they expire after 30 days).
Emails imported but dates show as today instead of original dates
Fix: This happens when PST files are corrupted. Run scanpst.exe (Inbox Repair Tool) on the PST file before importing. Repaired PSTs preserve original dates.
Duplicate emails after import
Fix: In the Outlook import wizard, select "Do not import duplicates." For network upload, check if the same PST was uploaded twice. Use the "Replace duplicates" option in the CSV mapping file.
Access denied error during network upload
Fix: Ensure your account has the Mailbox Import Export role in Exchange Online. Go to Exchange Admin Center > Roles > Admin Roles and add the role to your account.
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Frequently Asked Questions: PST Migration
QWhat is the best way to import PST files to Microsoft 365?
QHow long does PST import to Microsoft 365 take?
QCan I import multiple PST files to Microsoft 365 at once?
QWhat is the maximum PST file size for Microsoft 365 import?
QWill PST import preserve folder structure and dates?
QDo I need admin access to import PST files to Microsoft 365?
Have PST Files That Need Importing?
We handle PST imports as part of every migration project — from single-user archives to enterprise bulk imports across hundreds of mailboxes.