Stellar Converter for OST Corporate: Get Your Mail Out of an Orphaned OST File
Stellar Converter for OST Corporate is a $79 one-year Windows program that opens an Outlook offline data file (OST), including one you can no longer open in Outlook, and saves its mail, contacts and calendars to a PST or other formats. It suits IT staff and small business owners who have an orphaned or broken OST and need the mailbox back, and the free version shows you everything it found before you pay.
An OST is tied to one Outlook profile and one mailbox. Delete the account, lose the profile or have the Exchange server die, and Outlook won't open the file, even though your mail is still sitting inside it. Stellar Converter for OST reads the file without that profile and copies the contents out to something Outlook will accept.
Quick facts
- Version: 14.0.0.1, released July 2026
- Developer: Stellar Data Recovery (this product used to be called Stellar OST to PST Converter)
- Runs on: 64-bit Windows 11, 10, 8.1 and 8. There's no Mac version
- Reads: OST files from Outlook 2024, 2021, 2019, 2016, 2013, 2010 and 2007, including Exchange, IMAP and Microsoft 365 profiles
- Saves to: PST, MSG, EML, RTF, HTML and PDF
- Price: $79 for 12 months on one device
- Free version: scans and previews the whole mailbox, but saves nothing
- Refund: 30 days from purchase, first purchase only, with conditions (see below)
- What we checked: the installer on Stellar's server (18.8 MB, file version 14.0.0.1, dated August 14, 2026), the trial limits and Outlook requirement in Stellar's manual, Stellar's refund policy, and the $79 price and 12-month renewal on the order page on November 6, 2026. We didn't convert an OST ourselves, so the results below come from the reviewers and users quoted.
Before you buy: three things that catch people out
- You must have Outlook to save a PST. Stellar's manual says Outlook isn't needed to convert and preview, but it must be installed to use the save options.
- This is a yearly license, with an auto-renewal option at checkout. If you have one OST to rescue, make sure renewal is off. Stellar's refund policy doesn't cover renewals.
- Run the free version on your real file first. Stellar's refund policy refuses a refund if you bought without trying the evaluation version, and it also excludes "Special Offer" purchases. If the preview shows your mail, you know what you're paying for.
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Overview
The Corporate edition does one job: it turns a single OST at a time into something usable. You point it at the file or let it list the profiles on the PC, it scans, and you get a three-pane window that looks a lot like Outlook, with the folders on the left, the messages in the middle and the open message on the right. Deleted items that it finds show up in red. From there you save everything, or pick folders and individual messages.
You don't need the original profile or a connection to the Exchange server, which is the whole point. Microsoft's own answer to a bad OST is to delete it and let Outlook rebuild it from the server. That works only while the mailbox still exists on the server.
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The three-pane preview after a conversion: folders, message list and the selected message.
Features
Reads OST files Outlook won't open
Stellar Converter for OST handles orphaned, inaccessible and encrypted OST files, and files created by IMAP accounts, Exchange and Microsoft 365 profiles. You don't need the Outlook profile that created the file.
Finds the file for you
Stellar Converter for OST lists the OST files of the profiles configured on the PC. For a file copied somewhere else, you can browse to it or use the Find option to search a folder or drive. That helps, because the default home for these files is a hidden folder under AppData.
The start screen asks whether to list the Outlook profiles on this PC. Manual's image from version 13 Corporate.
Recovers every mailbox item, including deleted mail
Stellar Converter for OST extracts emails, attachments, contacts, calendars, tasks, notes and journals, and keeps the folder tree. It also lists deleted items it can still read, in red, and a "Do not convert Deleted Items" checkbox leaves them out.
Calendar entries get their own preview, with day, work week, week and month views. Manual's image from version 13 Corporate.
Save it all, or one message
Stellar Converter for OST Corporate saves to PST, MSG, EML, RTF, HTML or PDF. Filters narrow a save by date or sender, and Find Message searches on To, From, Subject and date, so you can right-click a single message and save only that.
Find Message searches the converted mailbox, and each result can be saved on its own. Manual's image from version 12.
Saves the scan so you can come back
Stellar Converter for OST can save its scan as a DAT file and load it later, on the same PC or another one. On a big file that means scanning overnight on one machine and saving the next day on the one that has Outlook.
Splits very large mailboxes
Stellar Converter for OST automatically splits the new PST at about 45 to 48 GB with Outlook 2010 or later, and about 18 GB with Outlook 2007, which keeps the output within what Outlook handles comfortably.
Real-World Uses
- A leaver's mailbox is gone. The account was deleted from Exchange or Microsoft 365, and the only copy left is the OST on their old laptop.
- The server died. Your Exchange host crashed or was hacked, and the cached OST on each PC is your newest copy of the mail.
- A broken profile. Outlook no longer opens the profile, or the file won't sync, and rebuilding would lose what never reached the server.
- One message for a legal or accounts request. You need a few emails out of an old OST as PDFs, not a whole mailbox.
Who It's For, and Who Should Skip It
Buy it if you have one or two OST files that Outlook can't open and the mail matters. A small office without a dedicated Exchange admin is the natural customer, and $79 is cheap against the cost of the lost mail.
Skip it if the mailbox still exists on the server: delete the OST, and Outlook will download a fresh copy for free. Skip Corporate if you have a batch of files or want to push them straight into Microsoft 365, because that's the Technician edition. And if you only need to read an old OST and never plan to use the mail in Outlook, Stellar's free preview may be enough to find what you're after, although you can't copy anything out of it.
Usage Guide
- Download and install the free version on a Windows PC, and copy the OST there if it's on another machine.
- Start Stellar Converter for OST and choose List Profiles, or choose Choose Manually to browse to the file. Click Find if you don't know where it is.
- Click Convert and wait for the scan to finish.
- Check the preview. Open a few messages, the calendar and the contacts.
- If it all looks right, buy a license and enter the activation key. You don't need to scan again if you saved the scan.
- Click Save Converted File, choose PST, and pick a location. Then open or import the PST in Outlook.
Where it falls short
- It can't rescue everything. Stellar's manual says an "Invalid OST file" error can mean the file is too badly damaged to convert. Trustpilot has a few buyers in that position, so trust the preview, not the marketing line about 100% precision.
- Large files are the weak spot in user reports. Stellar advertises no file size limit, but some Trustpilot reviewers describe trouble and one crash on larger OST files. Give it a PC with plenty of memory and disk space.
- Support is good, but you may need it. Many five-star reviews thank a named technician for getting the job done, which is reassuring and also a sign that the process doesn't always go smoothly alone.
- Contacts can seem to go missing. Stellar's manual has a whole FAQ on finding them after import, through Outlook's Advanced Find.
- Corporate has no batch mode and no direct export. Exporting to live Exchange or Microsoft 365, batch conversion and compacting are Technician features.
What Users Say
Reviews of this product are strongly positive on the whole, with a real minority who say it failed or that the refund was hard to get. Stellar as a company scored 4.8 out of 5 on Trustpilot from 5,601 reviews when we looked, and that figure covers all its products. Many of the warm reviews below are as much about the support staff as the software.
Trustpilot: buyers who got their mail back
Vigneshwaran Vijayakumar (June 20, 2025, 5 stars): "We manually loaded large OST files (over 3 GB), and the software handled the conversion without slowing down or crashing."
S A Abbas (November 7, 2025, 5 stars): "I used Stellar OST to PST conversion software which did the job it was meant to do."
Andy (September 18, 2025, 5 stars): "Swatantra did a wonderful job, gave me the opportunity to easily convert an orphaned OST."
Peggy (November 3, 2025, 5 stars): "Was very helpful in diagnosing that the OST file was corrupted. He also helped get the OST file repaired and converted."
Owen Lockwood (January 22, 2026, 5 stars): "Working to reinstate orphaned MS 365 email accounts, I had issues reconciling the Outlook Data Files."
Trustpilot: the critical side
ReviewerThree (May 19, 2026, 1 star): "I purchased Stellar Converter for OST. It did not work. I contacted support and asked for refund."
Gary (March 24, 2026, 4 stars, despite the wording): "the Stellar app is pretty terrible when it comes to having to work with ost files."
Raj (May 5, 2026, 3 stars): "I have a 13GB OST file which this software says works with "No File Size Limitations"."
Damon Kennish (December 8, 2025, 5 stars): "I still need to finish the conversion of a larger ost file. The software has just crashed during an attempt for this."
John Scott (August 21, 2024, 1 star): "Stellar Converter for OST does not load to 365 from domain computers."
Jon (September 9, 2026, 1 star) tried Stellar's web-based converter, a separate service: "Turns out at the end they only are willing to give you a preview of that file and not the actual file itself".
Hands-on reviews
TechyGeeksHome tested it and wrote that it's "reliable, fast, and accurate" and that "Even for occasional users with orphaned or encrypted OST files, it provides peace of mind knowing you can always access your mailbox data." Its only listed con: "The free version only allows preview, not PST export." The same review notes Auto Locate worked for standard folders, while "for files in custom locations, manual selection was necessary."
Rizonesoft walked through each feature and reported that the conversion kept the folder tree, formatting and attachments. It also warned that auto-locate "may face challenges in non-standard setups or environments with multiple Outlook profiles", and that "complex email formats or intricate attachments might not always be fully captured in the preview."
SoftwareTestingHelp called the support "pretty decent" and listed one con: "24/7 tech support would've been nice."
On Stellar's own page and G2
Daniel Beato, quoted by Stellar: "I have been using Stellar OST to PST converter since 2010 as an MSP provider using the Tech License and it has worked wonders for Outlook 2003 to 2016 conversions of OST Files."
On G2, a listing for the older product name showed 4.2 out of 5 from 11 reviews. Users there liked the conversion speed, and one complained that the program takes a while to load.
The themes: people like that it opens orphaned files with no profile, that the preview proves the mail is there, and that support staff step in when it gets stuck. The complaints are about large files, cases where it simply didn't work, and refunds. Stellar's policy does allow a refund when the product can't do the job and support has no fix, but it comes with the conditions above.
Comparisons
Stellar Converter for OST vs rebuilding the OST
Rebuilding is free and is the right answer when the mailbox still lives on the server. Stellar is what you buy when it doesn't, because a rebuild downloads the server's copy and an orphaned OST has no server copy to download.
Editions and Pricing
| Edition | Price | License | Adds |
|---|
| Corporate (this listing) | $79 | 12 months, one device | Converts one OST at a time to PST, MSG, EML, RTF, HTML or PDF, with filters and auto-split |
| Technician | $149 on Stellar's site | 12 months | Batch conversion, compacting and splitting PST files, export to live Exchange, Microsoft 365 and an Outlook profile |
| Toolkit | $199 on Stellar's site | 12 months | Everything in Technician, plus PST repair, merge, password recovery and undelete tools |
FAQs
Does Stellar Converter for OST need the original Outlook profile?
Stellar Converter for OST doesn't need the profile that created the file, or a connection to Exchange. It reads the OST directly, which is why it works on orphaned files. You do need Outlook installed on the PC where you save a PST.
Can Stellar Converter for OST open an encrypted OST file?
Stellar Converter for OST lists encrypted OST files among those it supports, and converts them to PST. As with any damaged file, check the free preview before you buy.
Will the free version of Stellar Converter for OST save anything?
The free version of Stellar Converter for OST saves nothing. It scans and previews the file, and saving needs an activation key. Some older reviews mention saving 20 items per folder, but Stellar's current pages describe preview only.
How big an OST file can Stellar Converter for OST handle?
Stellar Converter for OST has no stated size limit, and the manual covers files over 50 GB, with the new PST split at about 45 to 48 GB. Some users do report trouble on large files, so scan yours in the free version first.
What happens when the one-year Stellar Converter for OST license ends?
The Stellar Converter for OST Corporate license runs for 12 months, and you can turn auto-renewal off at any time. Anything you already saved to PST stays yours and opens in Outlook without Stellar.
Can I upgrade from Stellar Converter for OST Corporate to Technician?
Stellar says Corporate users can move up to Technician by contacting its support team. Stellar's site doesn't publish an upgrade price, so ask before you assume you'll only pay the difference.
Why did I get an "Invalid OST file" error in Stellar Converter for OST?
Stellar's manual gives three reasons for that error: the file is severely corrupted, it isn't a valid OST, or it couldn't be accessed. Copy the file to a local drive and try again. If it still fails, this tool isn't going to help with that file.
Does Stellar Converter for OST run on a Mac?
Stellar Converter for OST runs only on 64-bit Windows. To convert an OST from a Mac setup, copy it to a Windows PC or virtual machine that has Outlook installed.
System Requirements
- 64-bit Windows 11, 10, 8.1 or 8
- Intel-compatible x64 processor, including Parallels, Surface and Snapdragon systems per Stellar
- 4 GB of RAM (8 GB recommended)
- 250 MB of disk space for installation, plus room for the output
- Microsoft Outlook 2024, 2021, 2019, 2016, 2013, 2010, 2007 or Office 365 to save a PST
Conclusion
If your mail is trapped in an OST that Outlook won't open, and the server copy is gone, Stellar Converter for OST Corporate is worth $79. The one reason to buy it is the free scan: you see your actual mail before you spend anything, and that takes most of the risk out of it.
The main reason not to buy is that you may not need it. If the mailbox is still on the server, a rebuild is free. And if the preview doesn't show your mail, believe it and keep your money. Turn auto-renewal off unless you convert OST files regularly.
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