DataNumen OST to PST Converter: Turn an Outlook OST File Into a PST You Can Open
DataNumen OST to PST Converter is a $199.95 Windows tool that converts Outlook OST files into PST files, so the mail, calendar and contacts in an offline cache can be opened in Outlook or imported into a new profile. It's for people who are left with an OST file and no way to open it: a PC moved to a new account, a mailbox that was deleted on the server, or an old laptop's data you still need.
Outlook only opens an OST file through the account that created it. Take the file somewhere else and Outlook refuses it. A PST, on the other hand, opens anywhere, which is what this converter gives you.
Quick facts
- Version: 1.0, released October 20, 2024 (the product's first release)
- Developer: DataNumen, Inc.
- Platform: Windows, 32-bit and 64-bit
- Input: OST files from Outlook 97 to 2021 and Microsoft 365, for Exchange, Microsoft 365 and IMAP accounts (Outlook.com, Gmail, Hotmail)
- Output: PST in Outlook 97-2002 or Outlook 2003 and later format
- Price: $199.95 for one user, one-time, with no auto-renewal on the order page
- Trial: free demo; DataNumen's demos show a preview of the result or make a demonstration file, and the full version writes the complete PST
- Guarantee: 30 days
- What we checked: installer file version 1.0 (19.55 MB, digitally signed by DataNumen, Inc.) downloaded from the vendor, with an October 20, 2024 file date; the $199.95 order page price. We didn't convert an OST file. Checked on November 8, 2026.
Before you buy
- Know whether your OST is healthy or damaged. DataNumen sells a second product, DataNumen Exchange Recovery, at the same $199.95, and its own page sends you there for OST recovery. This converter is the one it recommends for converting.
- You may not need a converter at all. If the mailbox still exists on the server, adding the account to Outlook again downloads everything, and Outlook's own Export can write a PST for free.
- Close Outlook first. The tool needs Outlook and anything else that may hold the OST file shut down before it starts.
- Upgrades and support run for one month. After that you need the Annual Support and Maintenance Plan or a paid upgrade.
- A refund needs a reason. Refunds run for 30 days, but you must explain why in detail, and DataNumen may ask for the original file to verify it. The company offers to sign an NDA where needed.
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Overview
The program has four tabs: Convert, Batch Convert, Options and About. On the Convert tab you pick the OST file and where to save the PST, choose formats or leave both on Auto Determined, and click Start Convert. A 12-stage progress bar and a log show what it's doing.
The output goes to a new file called xxxx_recovered.pst beside the original, so Outlook.ost becomes Outlook_recovered.pst. Items keep their original folders, and anything it finds without a folder lands in folders named Recovered_Groupxxx.
The Convert tab in version 1.0: source OST, output PST, format boxes, the 12-stage progress bar and the log.
Features
Converts every kind of Outlook item
DataNumen OST to PST Converter carries over mail messages (plain text, RTF and HTML), attachments, embedded objects such as attached messages or Word and Excel files, folders, posts, appointments, meeting requests, contacts, distribution lists, tasks, task requests, journals and notes. Properties such as subject, sender, recipients and dates come along too.
Deleted items come back too
DataNumen OST to PST Converter also converts deleted items it finds in the OST: messages, folders, appointments, contacts and the other item types listed above.
Encrypted and very large OST files
DataNumen OST to PST Converter handles OST files with compressible or high encryption, even when you don't have the password. The vendor quotes a file-size limit of 16,777,216 TB, which in practice means no limit, and an option optimizes it for huge files.
Split output and pick the PST format
DataNumen OST to PST Converter can split the output into several smaller PST files once it passes a size you set, which helps with old Outlook versions and slow imports. You can write an Outlook 97-2002 PST or an Outlook 2003 and later PST, or let it match the Outlook on the PC.
The Options tab: huge-file optimization, PST splitting at a set size, fast scan, and a fix for Outlook's "Can't move the items" error.
Batch conversion
DataNumen OST to PST Converter has a Batch Convert tab where you add files by hand or search a drive for them, then convert the whole list in one run with a status for each file. That saves time when an IT team retires a batch of old PCs.
The Batch Convert tab, with Add Files and Search Files and a status column for each OST.
Benefits
- Mail that outlives the account. A PST opens in any Outlook profile, long after the Exchange or Microsoft 365 mailbox is gone.
- No server needed. The conversion works from the file alone.
- The original stays untouched. It writes a new PST and doesn't modify the OST.
Real-World Uses
- A departed employee's laptop. The Microsoft 365 license was removed, the mailbox deleted, and only the OST on the old laptop remains. Convert it and hand the PST to their manager.
- A new PC or new Outlook profile. Bring the cached mail across when you can't simply sync it again.
- A company leaving Exchange. Archive the cached mailboxes of old machines as PST files with Batch Convert.
- A Gmail or Outlook.com account set up as IMAP. Keep a local PST copy of what the OST holds.
Who It's For, and Who Should Skip It
It suits IT administrators and support staff who handle OST files from retired accounts and old machines, and home users who have only an OST file left from an old job or PC.
Skip it if the mailbox still exists on the server: sign in again and use Outlook's free Export to PST instead. If the OST is badly damaged rather than just orphaned, DataNumen points you to its Exchange Recovery tool, at the same price. If your problem is a corrupt PST, you need DataNumen Outlook Repair. And Mac users need a Windows PC, since this is Windows only.
Usage Guide
- Install the demo and close Outlook and any program that might be using the OST file.
- On the Convert tab, type the OST file name, browse to it, or use the search button to find OST files on the PC.
- Leave the source format on Auto Determined unless you know the Outlook version that made it. Auto takes a little longer, because it analyzes the file first.
- Check the output name (
xxxx_recovered.pst) and choose a PST format, or leave it on Auto Determined to match your Outlook.
- Click Start Convert and watch the progress bar. When it finishes, a message confirms the conversion.
- Open the new PST in Outlook with File, Open, Open Outlook Data File, or import it into your profile.
Where it falls short
- A brand-new product. Version 1.0 is the only release so far, from October 2024, and it has no independent reviews yet.
- An overlap you have to work out. The converter also lists support for corrupt OST files, while DataNumen's own page sends OST recovery to Exchange Recovery at the same price. The vendor doesn't explain the difference in detail, so ask before buying if your file is damaged.
- Free alternatives exist. When the account still works, Outlook does the same job for nothing.
What Users Say
We couldn't find any independent user reviews of DataNumen OST to PST Converter. The product only appeared in October 2024, and the review sites we checked list other vendors' OST converters. DataNumen's product page shows 4.90 out of 5 from 1,685 votes, a figure the vendor collects itself, so don't read too much into it.
What reviews of DataNumen's Outlook tools say
Testimonials for DataNumen Outlook Repair, a different product from the same developer that also writes recovered mail to PST, give an idea of what to expect from the vendor: people praise it for files Outlook's own tools couldn't handle and for its simple screen, while the complaints are about long run times on big files and a few leftover items to clean up. Treat that as a guide to the vendor's tools, not as reviews of this product.
Comparisons
DataNumen OST to PST Converter vs. DataNumen Exchange Recovery
Both cost $199.95 and both write OST content to a PST. DataNumen positions this converter for turning OST files into PST so you can open or import them, and Exchange Recovery (version 10.01) for recovering corrupt, oversized or unusable OST files. If your OST opens fine in its own profile and you just need it as a PST, the converter fits. If Outlook reports errors in the OST, start with the Exchange Recovery demo.
DataNumen OST to PST Converter vs. Outlook's Export
Outlook's Import/Export wizard can export a working account's mailbox to a PST at no cost. It needs the account to sign in. The converter is for when it can't.
Editions and Pricing
There's one edition. Volume licenses are cheaper per user, as listed on DataNumen's order page:
| User licenses | Price per license (US$) |
|---|
| 1 | 199.95 |
| 2 - 9 | 149.95 |
| 10 - 24 | 119.95 |
| 25 - 49 | 99.95 |
| 50 - 99 | 69.95 |
| 100 - 199 | 49.95 |
| 200 - 499 | 39.95 |
| 500+ | 29.95 |
FAQs
Can DataNumen OST to PST Converter convert an OST without the Exchange server?
Yes. DataNumen OST to PST Converter works from the OST file alone, so the original account or server doesn't need to exist any more.
Does DataNumen OST to PST Converter work with Microsoft 365 and Gmail OST files?
Yes. DataNumen OST to PST Converter lists Exchange accounts, Microsoft 365 accounts and IMAP accounts such as Outlook.com, Gmail and Hotmail among the OST types it converts.
Do I need the OST password to use DataNumen OST to PST Converter?
No. DataNumen OST to PST Converter converts OST files with compressible or high encryption even when you don't have the password.
Will the PST from DataNumen OST to PST Converter open in an old Outlook?
Yes, if you pick the Outlook 97-2002 output format. Old Outlook versions can't open the newer PST format, and the 97-2002 format has a much smaller size limit, so use the split option for a big mailbox.
Is DataNumen OST to PST Converter a subscription?
No. DataNumen OST to PST Converter is a one-time purchase. Free upgrades and support last one month, then you can buy the Annual Support and Maintenance Plan or pay for an upgrade.
Where do items without a folder end up after conversion?
DataNumen OST to PST Converter puts items it can't place in their original folder into folders named Recovered_Groupxxx in the new PST.
System Requirements
- Windows
- Intel or equivalent processor, x86 or x64
- 32 MB of memory minimum, 2 GB recommended
- 34.5 MB of disk space
Conclusion
Worth $199.95 if you have OST files whose accounts are gone and you need the mail as a PST, especially several at once. The reason to buy is that it works from the file alone, with batch conversion and PST splitting. The main reasons not to: Outlook does the job free while the account still works, and if your OST is damaged, DataNumen's own advice is Exchange Recovery at the same price. It's also a version 1.0 with no independent reviews, so run the free demo on your file first.
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