Written by Jennifer Walsh. Reviewed for technical accuracy by Shubham Dixit, Independent Expert in Email Forensics and Data File Conversion. Updated 9 October 2026.
Shubham is an independent external reviewer and not an employee of PCDOTS.
Quick answer. Kerio Connect keeps every mailbox on the server as .eml files, so there’s a free route. Add the Kerio account to Outlook over IMAP, let the folders sync, then use File, Open and Export, Import and Export, and export an Outlook Data File (.pst). Admins who want many mailboxes at once, or who only have the server files, can read the store with a converter instead.
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How do you export a Kerio mailbox to PST?
You export a Kerio mailbox to PST through Outlook, free, because of how Kerio stores mail. You don’t have to start with a paid tool, whatever a tool-first guide says. This guide shows how to export Kerio mailbox to PST, free with Outlook and in bulk with a tool.
Kerio Connect keeps every mailbox on the server as plain .eml files, the same single-message format Outlook understands. So the mail is reachable two ways. Connect the account to Outlook over IMAP and let Outlook pull the folders down, then export them to a PST. Or, if you run the server, read the .eml store with a converter.
The free Outlook route fits one or two mailboxes and doubles as the answer to using Kerio with Outlook 2016 or later. A converter fits an admin moving many mailboxes at once. Both are below.
People export for a few reasons. A PST opens in any Outlook on any Windows machine, it’s the format Microsoft 365 and Exchange import, and it’s a clean offline archive for retention or an e-discovery hold once you leave Kerio. Getting the mail into a PST keeps it usable long after the server is gone.
Kerio stores mail as .eml, so it reaches a PST through Outlook over IMAP, or through a converter reading the store.
“The thing most guides hide is that Kerio already stores every mailbox as .eml on the server, so nothing about the mail is locked. For a mailbox or two I just connect the account to Outlook over IMAP, let it sync and export a PST, no purchase needed. Where a converter earns its place is scale, an admin facing dozens of mailboxes or a case where you only have the server store and can’t sign in as the users. In my own migrations I always export one mailbox first and open the PST to check the folders and attachments before I trust the batch.” Shubham Dixit, Data File reviewer (draft, pending approval)
How does Kerio Connect store your mail?
Kerio Connect, now part of GFI, keeps mail on the server, not in one file on your PC. Knowing where it sits explains both routes below.
Where the mail lives
- One .eml per message. Every email is a separate .eml file, the same format Outlook can read, so nothing needs unlocking first.
- The store path. On the server, mailboxes sit under
store/mail/<domain>/<user>, with a folder for the Inbox, Sent and the rest, every one with its own index. - Two ways in. Reach it as a user through IMAP in Outlook, or as an admin straight from the store folder on the server.
So there’s no proprietary wall. A user exports through Outlook, and an admin can work from the .eml store. Here’s the free Outlook route first.
How do you export Kerio to PST with Outlook, free?
You connect the Kerio account to Outlook over IMAP, let it sync, then export a PST with Outlook’s own Import and Export wizard. This is the free route, and it’s the same setup people mean by using Kerio with Outlook 2016.
Here are the five steps.
- In Outlook, open File, Add Account, enter the Kerio email address and choose IMAP, with the Kerio server and SSL ports.
- Let Outlook sync the folders. A large mailbox takes a while, so give it time to finish.
- Open File, Open and Export, then Import and Export.
- Select Export to a file, then Outlook Data File (.pst), and select the Kerio account at the top with Include subfolders on.
- Choose a save location and finish. You now have a PST of the mailbox.
One honest note. IMAP syncs your mail folders. Calendars and contacts travel over CalDAV and CardDAV or the Kerio Outlook Connector, so if you need those in the PST too, add them before you export.
Add the Kerio account over IMAP, let it sync, open Import and Export and save an Outlook Data File.
What if you only have the server files?
Sometimes you can’t sign in as the user, you just have the Kerio server. That’s fine, the mailbox is right there as .eml files.
On the server, open store/mail/<domain>/<user> and you’ll see a folder for the Inbox, Sent and the rest, every one full of .eml files. Copy the user’s folder somewhere safe, then drag the .eml files into a folder in Outlook. Once they’re in Outlook, export a PST with the same Import and Export steps above. For a single mailbox this works without any extra software, and the next section covers doing it in bulk.
When does a converter help?
The free routes cover one or two mailboxes. A converter earns its place when an admin faces many mailboxes, or when only the server store is on hand and setting up Outlook per user isn’t practical.
PCDOTS Kerio Converter reads the Kerio .eml store on Windows and exports it to PST in bulk, keeping the folder tree and attachments, and it also outputs EML, MBOX or straight to Office 365. Follow these four steps.
- Install and run the converter, then add your Kerio store folder or mailbox files.
- Preview the folders and messages it reads.
- Select PST as the output, with the attachment option on.
- Convert, then open the PST in Outlook.
The converter route, the Kerio store to PST in bulk, with the folders and attachments kept.
One note for a big mailbox. A Unicode PST holds up to 50 GB, so a very large mailbox is cleaner split into a few smaller PSTs. The converter can split as it writes, which also keeps Outlook quick when you open the file.
Related reading, our guides to migrate AOL to Exchange Online and migrate Zimbra emails to Gmail. Want to read a mailbox file first? See view email headers of an MBOX file.
A server-bound mailbox versus a portable PST that any Outlook opens is why people export.
Which method should you use?
Use the free Outlook route for one or two mailboxes, and a converter for many mailboxes or a server-only job.
| Method | Best for | Good to know |
|---|---|---|
| Outlook over IMAP | One or two mailboxes | Free, also connects Kerio to Outlook 2016 |
| Server .eml files | No user login to hand | Drag from store/mail into Outlook, then export |
| Kerio Converter | Many mailboxes, bulk | Windows, reads the store, keeps attachments |
Not sure which row is you? Match your setup to the route below.
Match your setup to the route, a user exports through Outlook, an admin works from the .eml store, a bulk move suits a converter.
Key takeaways
- Kerio Connect keeps every mailbox on the server as .eml files, so a free route exists.
- Add the account to Outlook over IMAP, then export an Outlook Data File (.pst).
- No user login? The mailbox is under store/mail, drag the .eml into Outlook, then export.
- For many mailboxes or a server-only job, a converter reads the store and outputs PST in bulk.
Frequently asked questions
Can I export a Kerio mailbox to PST without a paid tool?
Yes. Connect the Kerio account to Outlook over IMAP, let it sync, then use File, Open and Export, Import and Export, and export an Outlook Data File. A converter is for bulk or server-only jobs.
How does Kerio Connect store mail?
On the server as individual .eml files, under store/mail then the domain and user, with a folder for the Inbox, Sent and the rest. There’s no single container file to unlock.
How do I connect Kerio Connect to Outlook 2016?
Add the account in Outlook over IMAP with the Kerio server and SSL ports. The folders sync down, and from there you can read the mail or export it to a PST.
Do my calendars and contacts come across?
IMAP brings your mail folders. Calendars and contacts travel over CalDAV and CardDAV or the Kerio Outlook Connector, so add those before you export if you want them in the PST.
How do I migrate Kerio to Exchange or Microsoft 365?
Export the mailbox to a PST first, then import that PST into Exchange or Microsoft 365. The PST is the bridge, and a converter can output straight to Office 365 for a bulk move.
Can I do this straight from the server?
Yes. Open store/mail, the domain and the user, copy that folder and drag the .eml files into Outlook, then export a PST. A converter does the same in bulk across many mailboxes.
Is there a size limit on the PST?
A Unicode PST holds up to 50 GB by default. For a very large Kerio mailbox, split it into smaller PSTs so Outlook stays quick and the file stays safe.
So how are you getting your Kerio mail into a PST?
Exporting a Kerio mailbox to PST is free for a mailbox or two, because Kerio stores the mail as .eml the entire time. Connect the account to Outlook over IMAP, let it sync, then export an Outlook Data File. Admins with many mailboxes, or only the server store, read the .eml folders with a converter instead. So how are you getting your Kerio mail into a PST, the free Outlook route, or a converter for the bulk?
