Introduction
What You'll Learn:- What EML actually is and which email clients open it natively
- Why Outlook's drag-and-drop method fails the moment you try to scale it
- How to convert a full PST archive to individual EML files in one shot
- What's inside an EML file — headers, MIME structure, what to expect
- Common conversion problems and exactly how to fix each one
Thinking of ditching Outlook? Or maybe you just need your old email archive somewhere that isn't tied to a single app? EML is your best bet. Thunderbird, Apple Mail, Windows Mail, eM Client — they all open it natively, no fuss. PST? Not so much. It's an Outlook-only situation until you convert it.
You're probably wondering — can't I just drag and drop? And yes, Outlook does have that. Classic Outlook lets you drag emails to your desktop and they save as .eml files. For five or ten emails, it's perfectly fine. But New Outlook dropped the feature entirely, attachments don't reliably survive the trip, and nobody's dragging 4,000 messages to a desktop folder one at a time. That's not a real workflow, and eventually you hit a wall with it.
This guide walks through both paths. You'll know what each method actually produces, when the manual route makes sense, and how to move an entire PST archive to individual EML files in one job.
What Is EML and Who Needs This Conversion?
Think of EML as the email world's common language. Not some locked-down proprietary format from one company — it's built on the RFC 5322 standard, the same spec that powers email across the internet. That's precisely why it's portable. Thunderbird, Apple Mail, Windows Mail, eM Client — they all read it natively because they're all built on the same standard.
Open an EML file and you'll find: a header block (From, To, Subject, Date, Message-ID), a blank line, and then the message body. Attachments are encoded inline using MIME — base64 blocks inside the same file, no separate folder needed. Everything travels together.
Here's who typically makes this conversion:
- People migrating from Outlook to Thunderbird or Apple Mail. Those clients don't read PST natively. EML is the bridge.
- IT teams decommissioning Outlook licenses. When the org moves platforms, the PST archives need to land somewhere that doesn't require Outlook to open them.
- Legal and compliance teams. One EML file per email means each message is independently searchable. Point an eDiscovery tool at a folder of EML files and it works — no email client required.
- Anyone who wants more resilient archiving. Think of PST like a single locked safe where everything lives together — if the safe is damaged, everything inside is at risk. EML is more like storing each email in its own small box. One box gets corrupted, that one email is gone, and the rest of the archive is completely fine. For long-term storage, that's a meaningful difference.
Worth knowing: EML stores email messages only. If your PST also contains contacts, calendar entries, or tasks, those won't convert to EML — you'd need a different format for those items.
EML is the right output when you're migrating to another email client or building a searchable archive. If you need visual formatting preserved for documentation purposes, look at HTML or PDF instead.
Outlook's Drag-and-Drop Method: What It Does and Where It Stops
Classic Outlook has a drag-and-drop path to EML. Open your PST via File → Open & Export → Open Outlook Data File. Select an email, drag it to a folder on your desktop. It saves as an .eml file.
For five or ten emails — pulling out a specific thread, grabbing a handful of messages from an old project — that works. Quick, no setup, files land exactly where you pointed them.
Here's where it breaks down.
New Outlook for Windows dropped the feature.
Microsoft removed drag-and-drop from the updated version. If you're on New Outlook, this method doesn't exist anymore. You'd need to switch back to Classic Outlook, which isn't always available.
Attachments don't always come through.
Oh, this is where drag-and-drop really lets you down. You save the EML, open it up, and then — nothing. No attachment. Or worse, it's there but corrupted and won't open. It's infuriatingly unreliable, especially when those attachments are exactly what you needed from the archive.
No folder structure.
Drag-and-drop has no awareness of your PST hierarchy. Inbox, Sent Items, subfolders — everything lands in a flat pile wherever you dropped it.
One at a time doesn't scale.
There's no batch mode that produces individual EML files. You either drag one email and get one file, or you look for another method.
There is a middle-path option worth knowing about: Thunderbird with the ImportExportTools NG add-on. Right-click any folder → ImportExportTools NG → Export All Messages in Folder → EML format. It's free and it works. But it requires importing your PST into Thunderbird first, which adds its own steps and gets complicated with larger files. Viable for a smaller one-off job. For anything large, it adds friction without adding reliability.
Drag-and-drop is only available in Classic Outlook for Windows. If you've updated to the new version, the feature is gone. Check which version you're running before you start.
How to Convert PST to EML (The Fast Method)
A dedicated converter reads the PST directly and writes each email as its own EML file — folder hierarchy preserved, attachments embedded, all message headers intact. One job, entire archive.
After wrestling with a lot of PST conversions, the tool I keep coming back to is MailExel. It doesn't need Outlook installed — a huge plus when you're digging through old archived PSTs on machines that haven't seen Outlook in years. Look, I've been in the trenches with some genuinely intimidating PSTs. One client migration involved a 14 GB monster — about 11,000 messages — and I was honestly sweating whether anything would make it out the other side intact. MailExel pulled it off. Folder structure, attachments, everything came through clean. That's the kind of relief you feel when you're dealing with someone's critical archive and you really can't afford to lose anything.
To follow these steps, you'll need the software installed. Download it below — takes about a minute, then come back and start at Step 1.
Launch the application and use Add Files to bring in your PST — or multiple files if you're working with several accounts. Everything loads as one job. Once added, your files show up in the main panel ready for scanning.
Once loaded, the software automatically scans everything in the PST: emails, contacts, calendars, notes, tasks. Nothing to do here. Most archives scan in a few minutes; larger PSTs take proportionally longer.
Before running anything, check the preview panel. Your folder structure appears with item counts — Inbox, Sent Items, every subfolder. Spend a minute here.
I had one job where the preview panel genuinely saved me. It flagged a shared calendar folder I hadn't even realized was in the PST — hundreds of old meeting invites, just sitting there. Good thing I caught it before running; otherwise I'd have had a messy archive and a frustrated client asking why meeting noise was mixed into their email history.
In the output settings, choose EML as the target format. Set a destination folder that's easy to find and has enough space. EML files are small individually, but a large PST produces a lot of them. The converter mirrors your PST folder structure in the output — the destination folder ends up looking like your original mailbox layout.
Start the export. The tool processes all selected folders and writes individual EML files to your destination with the folder hierarchy intact. Once it finishes, open a few output files in your target email client — Thunderbird, Apple Mail, or Windows Mail — and check that headers, body, and attachments look right. Don't skip this step.
What's Inside Each EML File
Before you load these files into a new client or hand them off to a legal team, it's worth knowing what you're actually looking at.
An EML file is plain text. Open one in VS Code or Notepad++ and you'll see this kind of structure:
From: sender@example.com To: recipient@example.com Subject: Q3 Budget Review Date: Tue, 8 Apr 14:22:00 +0000 MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="----=_NextPart_001" ------=_NextPart_001 Content-Type: text/plain; charset="UTF-8" Body of the email goes here. ------=_NextPart_001 Content-Type: application/pdf; name="budget_review.pdf" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="budget_review.pdf" [base64 encoded attachment data] ------=_NextPart_001--
So what are you actually getting in those EML files? A few things to know before you hand them off:
HTML emails keep their formatting.
Unlike TXT exports, EML preserves HTML structure. Bold text, tables, inline images — all of that survives. The MIME structure holds both a plain text version and an HTML version inside the same file.
Attachments are embedded, not stored separately.
EML encodes attachments inline as base64 blocks within the file. No separate attachment folder. Everything travels with the message, which is what makes EML self-contained in a way that TXT output isn't.
Headers include full routing metadata.
Beyond the basics — From, To, Subject, Date — you'll see Message-ID, X-Mailer, Received chain headers, MIME boundaries. All the transmission data that Outlook's reading pane hides from you is visible in the raw file. Useful if you're doing forensics, compliance review, or troubleshooting a delivery chain.
File size depends on attachments.
A plain text email might be 5 KB. One with a 10 MB PDF attached becomes roughly 14 MB in EML form — base64 encoding adds about 33% overhead. Plan storage accordingly if you're converting a large archive.
If you double-click an EML file in Windows Explorer and nothing happens, it just means no default app is set. Right-click → Open with → choose Thunderbird or Windows Mail, and check "always use this app." Or open the client first and import from there.
Common Problems and How to Fix Them
Running into problems after the conversion? These are the ones that come up most often, and most of them have a straightforward fix once you know what's actually causing them.
Attachments are missing from EML files.
With drag-and-drop, this is a known limitation — attachments frequently don't transfer cleanly. With converter-based exports, check the attachment settings before you run. Some tools have attachment export off by default or require it to be explicitly enabled. Re-run with that setting turned on.
Drag-and-drop isn't working in Outlook.
You're probably on New Outlook for Windows. Microsoft removed this feature in the updated version. Switch to Classic Outlook if it's still available on your machine, or skip the manual method entirely and use a converter.
EML files won't open on the destination machine.
No default app is set for .eml files. Right-click an EML file → Open with → Choose another app. Select Thunderbird or Windows Mail and check "Always use this app." Or launch the client first and use its File → Import option.
Folder structure is completely flat.
That's what drag-and-drop produces — no hierarchy, everything in one pile. A dedicated converter reads the PST folder tree and mirrors it in the output. If you've already run a flat export and need structure, re-run using the converter.
Fewer emails in the output than expected.
Two likely causes: Outlook was running during the export (it locks the PST, which causes partial reads — always close it first), or the PST has some corruption. Run Microsoft's ScanPST.exe — search "Inbox Repair Tool" in Windows — to check and repair the PST before converting again.
Characters showing up garbled in the output.
Encoding issue. The converter either defaulted to ASCII or handled UTF-8 incorrectly. Configure the converter to output UTF-8 and re-run. This shows up most with emails that contain accented characters, Arabic, Chinese, or other non-Latin scripts.
- Close Outlook completely before running any PST export.
- Work from a copy of the PST, not the live file.
- Check the preview panel to confirm folder counts match what you expect.
- Verify that attachment export is enabled in converter settings before running.
- Open a few output EML files in your target email client to confirm headers, body, and attachments are intact.
- If the PST is from a machine that crashed or was shut down improperly, run ScanPST.exe first.
- Keep the original PST until you've confirmed the output is complete.
Frequently Asked Questions
Can I convert PST to EML without Outlook installed?
Yes. A dedicated converter reads the PST file format directly without going through Outlook. This matters when you're processing archived PSTs from old machines, or when the whole point is to get away from Outlook entirely.
Will I get one EML file per email?
With a dedicated converter, yes — one EML file per email, organized into folders that mirror your original PST structure. Outlook's drag-and-drop also produces individual EML files, but only one at a time and with no folder hierarchy preserved.
Do EML files include attachments?
Yes, when you use a dedicated converter with attachment export enabled. Attachments are encoded inline inside the EML file using base64 MIME encoding — part of the file itself, not stored separately. Drag-and-drop does not reliably preserve attachments.
Which email clients can open EML files?
Most major clients: Mozilla Thunderbird, Apple Mail, Windows Mail, eM Client, Outlook Express, Windows Live Mail, and The Bat!, among others. Modern Outlook can open individual EML files but doesn't batch-import them natively without a workaround.
Can I convert EML files back to PST later?
Yes. Most dedicated converters that handle PST-to-EML also work in reverse. If you need to bring an EML archive back into Outlook, a converter can batch them into a PST. The round-trip generally preserves headers, body, and attachments cleanly.
Wrapping Up
PST to EML is a clean conversion when you use the right method. One file per email, folder structure intact, attachments embedded in each file. The drag-and-drop path works for a handful of emails in Classic Outlook — but it's not built for full archives, and New Outlook dropped it entirely.
For a full PST: load it into a dedicated converter, check the preview, select EML, run it. Before you hand anything off, open a few output files in your target email client and verify the body and attachments are there. Thirty seconds of spot-checking has caught real problems more than once.
Got questions about your specific setup? Drop them in the comments.
