Email Migration

How to Convert EML to PST: Outlook Drag and Drop, the Free Detours and the Batch Route

Leena Taylor Paul By Updated September 6, 2026 9 min read 3 screens
Quick Answer

To convert EML to PST for free, create a new Outlook Data File in classic Outlook, open the EML folder in Explorer and drag the files into an Outlook folder inside that PST. It works for a few hundred files in one folder. For thousands of EML files in nested folders, or when Outlook is not installed, an EML to PST converter such as Univik EML Converter does the job in bulk: it reads the whole tree and writes one PST file with the folders intact. Neither Outlook nor Office 365 can open a folder of EML files directly.

EML is the plain text email format almost everything can write: Thunderbird, Windows Live Mail, eM Client, Apple Mail (as .emlx), Mimecast and Proofpoint exports, eDiscovery packages and most mail servers. PST is the one format Outlook and the Microsoft 365 Import service actually take. Sooner or later a folder of .eml files has to become an Outlook Data File. This guide covers the free way inside Outlook, where the other free routes fall short and the bulk method for the big jobs.

Before You Convert EML to PST

Where did the EML files come from? Pick the card that fits and it takes you to the right method.

A few hundred EML files from one mailbox Thunderbird, Apple Mail or Windows Live Mail saved them into a folder or two. Outlook drag and drop handles this in an afternoon. Use Outlook drag and drop Thousands of EML files in nested folders An archive export from Mimecast, Proofpoint or Arctera. Or a whole Thunderbird profile. Folder structure matters and dragging folder by folder would take days. Go to the bulk route No Outlook on this PC, or the PST is for Office 365 The Microsoft 365 Import service takes PST only, and a migration workstation often has no Outlook. A converter that writes PST without Outlook closes both gaps. See how the converter does it
Before you start, get these four ready
  • The EML files in a folder you can browseUnzip archive exports first. Keep the folder names, because they usually carry the mailbox or the original Outlook folder.
  • Classic Outlook on Windows, for the free routeNew Outlook and Outlook on the web cannot open EML files into a PST. Drag and drop needs classic Outlook 2013, 2016, 2019, 2021 or Outlook for Microsoft 365.
  • Free disk space of about twice the EML totalA PST holds the same messages plus an index. 10 GB of EML becomes roughly 8 to 12 GB of PST, and Outlook needs working room.
  • A target size in mindIf the PST is bound for Office 365 keep it under 20 GB. For Mimecast 5 to 10 GB. For Outlook itself, 25 GB or less stays quick.
Five words this guide leans on
EML
One email per file, in the MIME format mail servers use (RFC 5322). Headers, body and attachments are all inside the one text file. Almost every client can write it.
PST
Outlook Data File, the container Outlook uses for a complete mailbox with its folder tree. It is what the Microsoft 365 Import service expects and what Mimecast lists first.
Drag and drop import
Dragging EML files from Explorer into an Outlook folder. Outlook reads each file and creates a message item. Free, but one folder at a time.
Winmail.dat
An attachment wrapper Outlook creates for rich text mail. If EML files from an Outlook sender carry it, the real attachments are inside and need unpacking.
Batch EML to PST converter
Software that reads a whole tree of EML files and writes PST files directly, with the folder names kept and no Outlook needed. The route for thousands of files.

Convert EML to PST with Outlook Drag and Drop in 4 Steps

This is the free method and it is fine for a few hundred files. Outlook does the conversion itself: every EML you drop becomes a message item inside the PST you choose.

1Step 1Gather the EML files in one folder

Put the files for one Outlook folder into one Explorer folder. If they came from Thunderbird, Apple Mail or an archive export they may already be sorted by mailbox folder, which is what you want. Give attachments that were saved separately their own subfolder so they do not get dropped as loose files.

You should seethe .eml extension on every file. Files with no extension or with .txt are still EML inside, so rename them before Outlook will recognise them.

Screen 1 of 3 · EML files in ExplorerWindows Explorer · recreated screen
Step 1An EML export folder. Select the files for one Outlook folder at a time.

2Step 2Set up the PST folders in a new Outlook Data File

In classic Outlook go to Home, New Items, More Items, Outlook Data File and save the PST where you want it. Right click the new data file in the folder pane and create the folders you need, such as Inbox 2024 and Sent 2024. Building the folders first means the messages land in the right place instead of one flat pile.

3Step 3Drag the EML files into the Outlook folder

Arrange Explorer and Outlook side by side. Select up to a few hundred files, drag them onto the target folder in the folder pane or into the message list, and release. Each file becomes a message. Work in batches of 200 to 500 because the client stalls on very large drops, and wait for the list to finish filling before the next batch.

You should seethe messages appear in the list with the original sender and subject. Open one that has an attachment and check the paper clip is there.

Screen 2 of 3 · Drag into OutlookClassic Outlook · recreated screen
Step 3Dropping six EML files onto the Inbox 2024 folder inside the new PST.

4Step 4Check dates, attachments and counts in the PST

Sort the folder by Received and confirm the received date on each message matches the original rather than today. Classic Outlook keeps the header dates from the EML in current versions, but older builds stamped the drop time, so check the first batch before you do the rest. Compare the item count in Outlook with the file count in Explorer. When they match, the folder is done.

Screen 3 of 3 · Converted messagesClassic Outlook · recreated screen
Step 4The converted messages with their original March 2024 dates and attachments intact.

What the Free EML to PST Routes Lose

Drag and drop is not the only free route people try. Here is where each one stops. If you only need to read a few messages rather than convert them, a free online EML viewer opens them in the browser with nothing to install.

Outlook drag and drop
The free way to import EML to Outlook. Faithful, but one folder at a time, a few hundred files per drop and classic Outlook required. Folder nesting has to be rebuilt by hand.
Windows Live Mail
Used to export EML straight to Outlook. Microsoft retired it in 2017 and it will not install cleanly on Windows 11, so this door is closed.
Thunderbird plus ImportExportTools NG
Imports the folders well, but Thunderbird cannot write PST. You end up with MBOX and still need a converter for the last step.
Free online converters
Upload limits of a few hundred megabytes, attachments often dropped and your mail on someone else's server. Not for company or legal data.

Batch Convert EML to PST Without Outlook

When the count is in the thousands, when folders are nested three deep or when the PC has no Outlook, dragging stops being a method. A batch EML to PST converter converts EML files to PST in one pass: it reads the whole export tree and writes the PST file directly.

  1. Add the EML folderOpen Univik EML Converter, choose Add Folder and select the top of the export. Every .eml in every subfolder is listed, with the folder path kept as the future Outlook folder.
  2. Pick PST and the split sizeSelect Outlook PST from the output list. If the file is headed for Office 365 or Mimecast, set the part size too and the converter writes numbered PST parts that stay under it.
  3. ConvertHeaders, dates, HTML bodies, inline images, attachments and message metadata are written into a Unicode PST as they were in the source. Winmail.dat wrappers are unpacked. The per-email log shows every file written.
  4. Open the PST in Outlook or import itAttach the PST in Outlook from the File menu, Open Outlook Data File. Or hand it to the Microsoft 365 Import service.

The tool runs offline on Windows and does not need Outlook installed, which is why it fits a migration workstation. For exports that came out of an archive platform rather than a mail client, the Email Archive Converter reads the same EML folders plus the platform's own manifest files.

A folder tree of EML files and no Outlook?

Convert thousands of EML files to PST in one run, folders intact

Univik EML Converter reads nested EML folders, keeps headers, dates and attachments and writes Outlook PST files split to the size you set. Runs offline on Windows with no Outlook required.

Free Download See All Features → Windows 11 / 10 · runs without Outlook · the trial writes a sample PST from each folder for you to check first

EML to PST Method Comparison

MethodCostBest forKeeps foldersNeeds OutlookSplit for import
Outlook drag and dropFreeUp to a few hundred files per folderManualClassicNo
Thunderbird + ImportExportTools NGFreeGetting EML into MBOX, not PSTYesNoNo PST at all
Free online converterFreeA handful of personal messagesNoNoNo
Univik EML ConverterTrial, then licenceThousands of files in bulk, nested folders, Office 365 or Mimecast importsYesNoYes

After the EML to PST Conversion

You will know the conversion worked when
  • Outlook attaches the PST from File, Open Outlook Data File and the folder tree matches the source folders
  • Item counts per folder match the file counts, and the Received column shows original dates
  • Messages with attachments show the paper clip, and one HTML message with inline images renders as it did in the source

If the PST is going to Office 365, keep it under 20 GB and add it to a mapping file as described in how to import PST to Office 365. If it came out of an archive platform, the wider plan lives in the email archive migration guide. And if a few loose EML files are all you need inside Outlook, the lighter route is importing EML files into Outlook directly.

Fix Common EML to PST Problems

EML conversions fail in three familiar ways. The red box names the symptom and the green text below it is the fix.

You seeDropped messages show today's date instead of the original
Do thisAn older Outlook build stamped the drop time. Update Outlook, or use a converter, which writes the header dates into the PST.
You seeAttachments are missing or a winmail.dat file appears
Do thisThe EML carried a TNEF wrapper from an Outlook sender. A batch converter unpacks it; for a handful of messages open winmail.dat with a free TNEF viewer and save the files.
You seeOutlook freezes on a large drop
Do thisToo many files at once. Close Outlook, run ScanPST on the new PST if it will not open, then drag in batches of 200 to 500. For anything over a few thousand files, switch to the batch route.

Not sure whether your EML folder will convert cleanly? Zip a dozen files including one with attachments and send them to our support team. We will run them through and tell you what to expect before you buy anything.

EML to PST questions

Classic Outlook opens a single EML file when you double click it, but there is no menu command to import EML to Outlook from a folder. Dragging the files into an Outlook folder is the only built-in way to convert EML to PST, and it works one folder at a time.

Yes. Create an Outlook Data File in classic Outlook and drag the EML files into it from Explorer. It is free and keeps the message content, but it is manual, needs Outlook installed and does not keep nested folders without rebuilding them by hand.

Use a converter that writes PST files directly, such as Univik EML Converter. It reads the EML folder tree and writes an Outlook Data File with the folders intact, no Outlook or Office 365 licence needed on that PC.

Yes. Export the Thunderbird folders as EML files with the ImportExportTools NG add-on, then convert that folder to PST. Thunderbird itself cannot write PST files.

When the EML files are complete, yes. Headers, sent and received dates, HTML bodies and attachments are all inside each file and are written into the PST. Winmail.dat wrappers are the one exception and need unpacking.

Not as EML. The Import service in Microsoft 365 reads PST and nothing else, so the EML folder has to become a PST first. Keep each PST under 20 GB and then run the import job.
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 Outlook behaviour in this guide was checked on classic Outlook for Microsoft 365 on Windows 11, and the screens are recreated so the labels match what you will see. Last verified September 2026. Need a hand? Contact our support team.

Sources checked: Microsoft Support, Import and export Outlook email · Microsoft Learn, Overview of importing PST files to Microsoft 365 · RFC 5322, Internet Message Format · Mozilla Support, Import settings and data into Thunderbird

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