Migrating PST to Office 365
Moving PST files into Microsoft 365 (Office 365) is one of the most common enterprise email migration tasks. Microsoft offers built-in methods, and third-party tools provide alternatives with different trade-offs.
Comparison Table
| Method | Cost | Complexity | Max File Size | Speed | Best For |
|---|---|---|---|---|---|
| Outlook desktop import | Free (with license) | Low | ~20 GB practical | Slow | Individual mailboxes |
| Network upload (Microsoft) | Free (with license) | High | 20 GB per PST | Moderate | Bulk enterprise import |
| Drive shipping (Microsoft) | $2/GB | High | No limit | Slow (shipping) | Very large datasets |
| BitTitan MigrationWiz | Per-mailbox fee | Medium | No limit | Moderate | Multi-source migration |
| MailtoPst + IMAP | Freemium | Low-Medium | 50 GB | Moderate | Cross-format flexibility |
| CodeTwo | Per-mailbox fee | Medium | No limit | Moderate | Exchange-to-365 |
Microsoft Built-In Methods
Outlook Desktop Import
Import PST directly via Outlook connected to Microsoft 365. Simple but slow — suitable only for individual mailboxes under 10 GB.
Pros: Free, simple. Cons: Very slow, manual, impractical at scale.
Network Upload
Upload PSTs to Azure Blob storage, then create import jobs via the Microsoft 365 compliance center.
Pros: No per-mailbox fees, handles bulk imports. Cons: Complex setup, requires Azure AzCopy, CSV mapping files, and admin center access. Limited to 20 GB per PST.
Drive Shipping
Ship physical hard drives to Microsoft for ingestion.
Pros: No bandwidth constraints. Cons: $2/GB, slow turnaround, complex logistics.
Third-Party Tools
BitTitan MigrationWiz
A popular cloud-based migration platform supporting multiple sources and destinations.
Pros: Multi-source support, cloud-based, good reporting. Cons: Per-mailbox licensing, can be expensive at scale, learning curve.
CodeTwo Office 365 Migration
Focuses on Exchange-to-365 and PST-to-365 migrations.
Pros: Purpose-built for Office 365, good support. Cons: Windows only, per-mailbox pricing, enterprise-focused.
MailtoPst Conversion Approach
For PST files that need format transformation before import, MailtoPst provides a flexible path:
- Convert PST to EML for IMAP-based import
- Use an IMAP client to upload to Microsoft 365
- Alternatively, use MailtoPst for pre-processing (format normalization, splitting) before using Microsoft’s native import
Pros: Format flexibility, GDPR-compliant, no per-mailbox fees, works from any platform. Cons: Indirect path, requires IMAP step for non-PST imports.
Verdict
For direct PST to Microsoft 365: Use Microsoft’s network upload for bulk imports or Outlook desktop import for individual mailboxes. These are built-in and free with your license.
For format flexibility: When your source data is not in PST format, or when you need to pre-process files, MailtoPst shines. Convert MBOX to PST or convert OST to PST first, then use Microsoft’s import methods.
For multi-source enterprise migrations: BitTitan or CodeTwo handle complex scenarios with reporting and project management features.
Try MailtoPst for pre-migration conversion →
FAQ
Can I import PST to Office 365 for free?
Yes. Microsoft’s network upload method is included with your Microsoft 365 license. Outlook desktop import is also free but much slower. Both require admin access to the Microsoft 365 tenant.
What is the fastest way to import PST to Office 365?
Network upload is the fastest built-in method. For very large datasets (1+ TB), drive shipping avoids bandwidth constraints. Third-party tools like BitTitan can parallelize the process for faster throughput.
Can I import MBOX to Office 365?
Not directly. Convert MBOX to PST first using MailtoPst, then import the PST using any of the methods above.