How to Import PST to Office 365 by Network Upload or Drive Shipping

You have a stack of PST files. Maybe they came from staff who left, from an old Exchange server or from an archive platform you are leaving. Office 365 will take them, but only through the Import service and only as PST. Whether you import PST files for three leavers or three hundred mailboxes, the route is the same. This guide walks through both routes with the screens you will see, the mapping file that trips most people up and the rules that decide whether the job runs in a day or stalls for a week.

Before You Import PST to Office 365

• Time1 to 3 days
• DifficultyMedium
• CostFree (upload)
• Runs onBrowser + Windows

Pick the card that matches your situation. It jumps you to the route that fits.

Import PST to Office 365 by Network Upload in 6 Steps

Network upload is free, needs no hardware and suits most jobs. To import PST files this way you do Steps 1 and 3 once per tenant. Steps 2, 4, 5 and 6 repeat for every batch of PST files.

1Step 1Open the Import page in the Purview portal

Sign in to the Microsoft Purview portal with the account that holds the Mailbox Import Export role. Open Data lifecycle management, then Microsoft 365, then Import. The page lists every import job the tenant has run with its status. Click New import job.

You should seethe New import job button active. If it is greyed out, the role is missing. Role changes can take up to an hour to apply.

2Step 2Name the PST import job and choose Upload your data

Give the PST import job a short lowercase name with no spaces, such as archive-batch-03. On the Do you want to upload or ship data? page pick Upload your data. The other option, shipping hard drives, is covered in section 3.

3Step 3Copy the SAS URL and download AzCopy

The Import data page lists the upload steps. Click Show network upload SAS URL, then Copy to clipboard, and paste it somewhere safe. This URL is unique to your tenant and anyone holding it can write to your import storage. Then click Download Azure AzCopy. Use this exact copy of AzCopy. Microsoft does not support other versions for the Import service. It is a single .exe with nothing to install.

You should seea long URL that starts with https and contains ingestiondata. Leave the two checkboxes at the bottom unticked until your files are uploaded.

4Step 4Upload the PST files with AzCopy

On a Windows PC or server that can see the PST folder, open a command prompt in the folder where you saved azcopy.exe and run one command. The source is the folder holding the PST files. The destination is the SAS URL in quotes.

azcopy.exe copy "\\FILESERVER1\PSTs" "https://3c3e...blob.core.windows.net/ingestiondata?sv=...&sig=..."

Subfolders are copied too, because --recursive is on by default. If you want the files in their own subfolder in Azure, add it after ingestiondata in the SAS URL, for example ingestiondata/batch03. Note the exact spelling. You will need the same case later in the mapping file. When AzCopy finishes it prints a summary with the number of files transferred and any failures. Go back to the portal and tick I'm done uploading my files and I have access to the mapping file.

You should seeNumber of File Transfers Completed equal to the number of PST files, and Number of File Transfers Failed at 0. If a transfer failed, run the same command again. AzCopy skips files already there. To see the uploaded files with your own eyes, open the same SAS URL in Azure Storage Explorer (a free Microsoft tool) and browse the ingestiondata container.

5Step 5Submit and validate the mapping file

Click Next and on the Select mapping file page upload the CSV that tells the service where to import PST data. Click Validate. The file name turns green when every row passes. If it turns red, click View log, fix the rows it names and upload again. Section 4 explains every column. The two mistakes that cause nearly all validation errors are a file name whose case does not match the uploaded file and a mailbox address that does not exist yet. A third is Excel itself: some regional settings save the CSV with semicolons, so open the file in Notepad and check the separators are commas before you upload.

6Step 6Let the analysis run, then filter and import the PST data

Review the job and save it. The status changes to Analysis in progress while Microsoft scans the PST files for age, item type and size. When it reads Analysis completed, open the job. You get a choice: import everything, or open Filter your data to drop items older than a date or skip categories such as junk. Click Import to Microsoft 365. This is the moment Office 365 imports the PST data into each mailbox. Progress shows per file, and the job ends at Complete.

You should seethe imported folders in each user's mailbox under the TargetRootFolder you set, or in a folder called Imported when you left that column blank. That is a finished import PST to Office 365 job.

Drive Shipping to Office 365, When and How

Drive shipping to Office 365 exists for one case: you need to import PST files measured in terabytes, more data than your line can push in a reasonable time. A 2 TB archive on a 50 Mbps upload takes about four days of non-stop transfer. At 10 TB and above, or from a site with a poor connection, a disk in a courier box wins. Microsoft charges a per gigabyte fee for the service and you supply the drive and the courier account.

1. Create the job and pick Ship hard drivesSame wizard as Step 2 above, second option. Download WAImportExport.exe from the job page. The PST files go on the drive instead of over the wire, but the import job in Office 365 is the same.
2. Prepare the driveRun WAImportExport.exe PrepImport with a journal file name, the drive letter, a session name, the PST source folder and /encrypt. It formats, encrypts and copies in one go. Repeat without the drive letter and encrypt switches to add more folders to the same drive.
3. Upload the journal files and shipAdd one journal file per drive in the wizard and validate. Pack the bare drive in an anti-static bag without the SATA to USB adapter. Put "Microsoft 365 Import Service" in the address line.
4. Enter the tracking numberInside 14 days, or the job expires and you start again. Then submit the mapping file when the portal asks for it.

The PST Mapping File Explained

The Office 365 PST mapping file is a plain CSV with a header row and one row per PST. Microsoft publishes a sample you can download from the wizard. The columns below are the ones that matter for mail. The three SharePoint columns stay blank.

Two practical habits save hours on every PST import to Office 365. Keep one mapping file per batch and name it after the job. Test with a two row file first, so a column mistake shows up on two PSTs rather than two hundred.

One Small PST? Import It into Office 365 with Outlook Instead

The Import service is built for admins and batches. If you are one person with one PST from an old computer, Outlook does the job without any of the above. Open Outlook signed in to your Office 365 account, go to File, Open & Export, Import/Export, pick Import from another program or file, then Outlook Data File (.pst), browse to the file and choose the mailbox as the destination. Outlook uploads the items to the cloud mailbox in the background. It is slow for anything over a few gigabytes and it counts against the mailbox quota, so it suits a personal archive, not a company migration.

When Your Archive Gave You EML or MSG, Not PST

This is the wall many migrations hit. You leave Mimecast, Proofpoint, Arctera or an on-premises archive and the export is thousands of loose .eml or .msg files, sometimes with an EDRM XML file next to them. The Office 365 Import service does not read them. A Microsoft forum thread sums it up: a company with 200 GB of .eml from an online archive asked how to get it into Office 365 and the answer was convert to PST first, keep each file under 20 GB and batch them.

1. Open the export folder in Univik Email Archive ConverterUse Add Folder on the unzipped export. The tool walks every subfolder, picks up each EML and MSG file and keeps the folder names, which usually map to users or dates.
2. Pick PST and set the split sizeChoose Outlook PST as the output and set the split size below 20 GB, so every file meets Microsoft's limit without a second tool. Folder structure, headers, dates and attachments carry across.
3. Name the PST files for the mapping fileOne PST per mailbox named after the user, such as annb.pst, makes the mapping CSV a copy and paste job. Journal exports become one PST for the journal mailbox.
4. Open one PST in Outlook, then uploadConfirm folders and attachments look right, then go back to Step 4 above and run AzCopy on the new folder.

The converter runs offline on your PC, so archive data never leaves your network before it goes to Microsoft. It reads exports from Mimecast archive exports, Proofpoint archive exports, Enterprise Vault PST exports, Google Vault MBOX exports and other platforms. For plain folders of loose files, the single-format EML converter and MSG converter do the same PST job; the step-by-step guides are convert EML to PST and convert MSG to PST. For the Arctera and Veritas eDiscovery case, see how to export Arctera eDiscovery email to PST.

After the Office 365 PST Import

Three things happen behind the scenes after a PST import to Office 365 that are worth knowing before users start asking questions.

Fix Common Office 365 PST Import Problems

Three things stop most attempts to import PST to Office 365. Match the symptom in the red box, then apply the fix under it.

Stuck on the conversion side, with EML or MSG folders that will not turn into clean PST files? Zip a dozen messages from the export and send them to our support team with the source platform name. We will tell you which route fits before you buy anything.

Office 365 PST Import Questions

Leena Taylor Paul

Written and maintained by Leena Taylor Paul and the Univik team, developers of Windows data conversion and recovery software since 2013. The Import service steps, limits and mapping columns in this guide were checked against Microsoft's current documentation, and the screens are recreated from the Purview portal so the labels match what you will see. Last verified September 2026. Need a hand? Contact our support team.

Sources checked: Microsoft Learn, Overview of importing PST files · Microsoft Learn, Use network upload to import PST files · Microsoft Learn, Use drive shipping to import PST files · Microsoft Q&A, Import legacy email archive into Office 365

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