How to Import PST files to Microsoft 365

Leena Taylor Paul
Updated: May 13, 2026 • Import • 9 Min Read

Summary: To import a PST file to Microsoft 365, you have four reliable options. If you just want to read the file first, see how to open a PST file without Outlook. First, for a single PST under 50 GB, use Outlook desktop’s File > Open & Export > Import/Export wizard while signed in to your Microsoft 365 account. Next, for bulk admin migration, use the free Microsoft 365 Network Upload service in the Compliance portal with AzCopy. Then, use Drive Shipping when you cannot upload over the internet. Finally, use a third-party PST importer for a GUI workflow without admin access.

Outlook wizard suits a single user importing a PST under 50 GB.
Network Upload is free and best for IT teams importing multiple PSTs.
Drive Shipping is the only path when your upload link is too slow.
A third-party tool works when you do not have Global Admin rights.

Why Import PST files to Microsoft 365?

Outlook stores email locally as PST (Personal Storage Table) files. This works well for a single desktop. However, it creates problems the moment you need cloud access, mobile sync, or team sharing. If your source mail lives in a different format, you can first open Maildir files in Outlook and export them to PST before this import.

Microsoft 365 fixes those gaps. Every mailbox lives on Exchange Online with a 50 GB to 100 GB quota. In addition, you get server-side rules, shared calendars, and access from Outlook on the web, mobile, and desktop without manual sync.

Importing a PST moves your historical mail into the cloud, so everything lives in one place. Microsoft offers two official import paths, and the wider ecosystem adds a couple of practical alternatives. Therefore, pick the one that matches your mailbox size, admin access, and timeline.

Before You Start: Prerequisites

An active Microsoft 365 mailbox (Business Basic, Business Standard, Enterprise, or any plan with Exchange Online).
The PST file or files on a local drive, ideally under 50 GB each.
Outlook desktop (2016 or newer) for Method 1.
Global Admin or the Mailbox Import Export role in Exchange Online for Method 2 and Method 3.
A recent copy of the PST kept on a backup drive before you start.

Method 1: Outlook Desktop Import/Export Wizard

This is the simplest path for a single user. It suits a PST under 50 GB going into your own Microsoft 365 mailbox.

Open Outlook desktop. First, confirm your Microsoft 365 account is added (File > Add Account if not).
Go to File > Open & Export > Import/Export.
Choose Import from another program or file and click Next.
Select Outlook Data File (.pst) and click Next.
Browse to the PST file. Then choose Do not import duplicates to avoid copies in your existing folders.
Pick your Microsoft 365 mailbox as the destination folder and click Finish.

Outlook copies the messages to Exchange Online in the background. The first sync of a large PST may take a few hours. Therefore, watch the send/receive status bar and leave Outlook open until the upload queue is empty.

Method 2: Microsoft 365 Network Upload (Free, Admin)

Network Upload is Microsoft’s free admin-grade import path. It uploads PST files to a temporary Azure storage area. Then it imports them into the target mailboxes based on a CSV mapping file. As a result, it suits IT teams importing PSTs for multiple users at once.

Step 1: Get the SAS URL

Sign in to the Microsoft Purview compliance portal with a Global Admin account.
Open Data lifecycle management > Import > Import PST files.
Click New import job. Name the job in lowercase letters with no spaces, then choose Upload your data.
Copy the SAS URL shown on the next screen. Keep it private, because anyone with the URL can write to the storage area.

Step 2: Upload PSTs Using AzCopy

Download the latest AzCopy tool from Microsoft and unzip it to a folder.
Open a Command Prompt and change to the AzCopy folder.
Run azcopy.exe copy "C:\PSTs\*" "[SAS URL]" --recursive=true, replacing the SAS URL with the one you copied.
Wait for the upload to finish. AzCopy shows live transfer speed and a completion summary.

Step 3: Create the Mapping CSV

The mapping file tells Microsoft 365 which PST belongs to which mailbox. Create a CSV with these columns: Workload, FilePath, Name, Mailbox, IsArchive, TargetRootFolder, ContentCodePage, SPFileContainer, SPManifestContainer, SPSiteUrl.

For each PST, fill in Workload = Exchange, Name = filename.pst, and Mailbox = user@yourdomain.com. In addition, leave the SharePoint columns empty for mailbox imports.

Step 4: Start the Import Job

Return to the import job in the Compliance portal.
Tick I’m done uploading my files and I have access to the mapping file.
Upload the CSV and validate it. Fix any rows the validator flags.
Click Submit. Microsoft analyzes the data, then prompts you to set filters (date range, folder exclusions) before the actual import starts.
Click Import to Office 365 when ready. The job runs in the background and emails a completion report.

Method 3: Drive Shipping (Offline Media)

If your total PST size runs into hundreds of gigabytes and your upload link is slow, Drive Shipping is the answer. You copy the PSTs to an encrypted hard drive and physically mail it to a Microsoft data center.

Microsoft charges a per-gigabyte fee plus return shipping. The workflow uses the same Compliance portal import job. However, you select Ship hard drives to Microsoft instead of Upload your data. Note: Drive Shipping is available in a limited set of regions, and pricing varies. Therefore, check the latest Microsoft documentation before you commit.

Method 4: Third-Party PST Importer Tool

If you do not have Global Admin access, or you need to import PSTs from a non-admin desktop, a third-party importer is the answer. The 4n6 Email Converter is one option that handles PST to Microsoft 365 imports directly with mailbox credentials.

Download, install, and launch the application on a Windows PC.
Click the Open tab to load your source data.

open-tab-pst-importer

Choose Email Data File, then select Outlook OST / PST Files and click Choose from a folder.

select-outlook-pst-files

Select the PST files you want to import and click Open to load them.
Preview the messages and attachments before you import.

preview-pst-files

Click the Export tab and choose Office 365 (the destination is the same Microsoft 365 mailbox).

export-to-microsoft-365

Enter the Microsoft 365 email address and password, then click Save.

enter-microsoft-365-credentials

The tool authenticates against Microsoft 365 and uploads each PST folder. As a result, a completion notice appears once every selected file is imported.

Which Method Should You Choose?

Single user, under 50 GB: Method 1 (Outlook Import/Export). Fastest setup, no admin role required.
Multiple users, bulk import: Method 2 (Network Upload). Free, scriptable, official.
Hundreds of GB, slow connection: Method 3 (Drive Shipping). Slowest path, but bypasses bandwidth limits.
No admin access, want a GUI: Method 4 (third-party tool).

Common Errors and Fixes

“Cannot create new file” in Outlook

The PST is over 50 GB. Therefore, split it into smaller PSTs using Outlook’s archive feature before importing.

SAS URL expired

SAS URLs are valid for 30 days only. Generate a new one from the Compliance portal, then resume the AzCopy upload.

CSV validation fails

The most common cause is a trailing space in the Mailbox column or a column header mismatch. As a result, open the CSV in a plain text editor and check the columns row by row.

Import skipped messages

Microsoft 365 rejects messages with attachments over 150 MB. Before import, you can also open attachments in a PST file without Outlook to inspect what is oversized. If you only need the attachment binaries, you can open the MSG files without Outlook and save attachments directly. Therefore, save oversized attachments to OneDrive (or first extract all attachments from the PST file), link them inside the message, then retry.

Items show today’s date

This happens when you used Move instead of Import in Outlook. Re-import using the wizard to preserve original timestamps.

Features of the 4n6 PST Importer

Batch PST Import: load multiple PST files in a single session, then import them all into the same Microsoft 365 mailbox without restarting the tool.

PST Preview: view every email body and attachment before you import. This helps you filter out personal mail from a work PST or vice versa.

Advanced Search: filter by sender, subject, or date range before importing. As a result, you save time when you only need a slice of a larger PST.

Selective Folder Import: pick specific folders such as Inbox, Sent, or Archives, rather than the entire PST tree.

Frequently Asked Questions

Can I import a PST file directly through Outlook on the web?

No. Outlook on the web does not support PST import. Therefore, you need Outlook desktop, the Microsoft 365 Network Upload service, or a third-party tool.

How long does a Network Upload import take?

Upload time depends on your bandwidth. However, the import itself typically processes 10 to 25 GB per hour once the PST is in Azure storage.

Is the Microsoft 365 Network Upload service free?

Yes. Network Upload has no per-GB fee. In contrast, Drive Shipping costs around $2 per GB at the time of writing.

Will the PST file be deleted from Azure storage after import?

Yes. Microsoft deletes uploaded PSTs from the Azure storage area 30 days after the import job completes.

Final Thoughts

Importing a PST file to Microsoft 365 is straightforward once you pick the right method. First, use Outlook’s Import/Export wizard for a single mailbox. Next, choose Network Upload for bulk admin imports. Then, use Drive Shipping for very large datasets on slow connections. Finally, fall back to a third-party tool when you need a GUI without admin permissions. Whichever path you choose, keep a copy of the original PST on a backup drive until you have verified that every folder is present in Microsoft 365.