Verdict: Stellar Converter for OST is worth considering when you have an inaccessible Outlook OST file and cannot recover the mailbox from its server. The online version suits an occasional conversion when you are comfortable uploading the file. The Windows desktop app is the more practical starting point when you need local processing, mailbox preview and selective export.
I tested Stellar’s online converter and Windows desktop application. The online walkthrough used a 286 MB OST file; the desktop evaluation covered locating an OST, previewing mailbox contents and selecting folders. The useful distinction is how you work with the mailbox, rather than treating every edition as the same product.
Before you start: keep the original OST unchanged and work on a copy. Only process mailboxes you are authorized to access. For work email, ask your administrator whether a server-side export or restore is available before uploading a mailbox to an external service.
Online converter: a straightforward upload workflow
The online converter starts with a sign-in screen, followed by file upload, conversion and download. In my test, that made the route easy to follow without installing a desktop application. It is a browser-based interface to an upload service: the OST leaves your device, so it is not browser-only local processing.
The account requirement is an extra step for a one-off job. Upload time also becomes part of the task, which matters more with a large mailbox or a slow connection. Check the file-size allowance, conversion allowance and price on the plan you select before uploading.
Desktop app: preview the mailbox before exporting
In the Windows application, the profile selection and file-browse options give you two ways to locate the OST. The preview then puts folders and messages into a familiar mailbox layout. That is the part I found most useful: you can look for the folders you need before deciding what to export.
Selective folder export is useful when the job is smaller than the mailbox. You can focus on the relevant folders instead of treating every newsletter and old attachment as part of the deliverable. The desktop edition comparison explains which license includes the export formats, batch processing or migration tools you need. Do not assume the lowest-priced edition includes them all.
Online or desktop: which should you choose?
- Choose online for a one-off file when its size fits the selected plan and external processing is acceptable. Allow time for the upload as well as conversion.
- Choose desktop for more control over locating files, previewing the mailbox and selecting output. Confirm Windows compatibility and the required license first.
- Ask your administrator first if the mailbox still exists in Microsoft 365 or Exchange. Restoring or exporting that copy may be preferable to converting an incomplete local cache.
Limits that matter before paying
A readable preview is encouraging, but inspect the saved output too. Check important attachments, calendar entries, contacts and representative messages against the source you expect. Keep the original until you are satisfied with the result. An OST may not contain items that were never synchronized to that computer.
My hands-on use supports the workflow observations in this review, not a promise that every damaged mailbox will convert or that every file will finish in a set time. For a critical recovery, try a representative copy before buying a larger license or committing several mailboxes.
For confidential email, the online service’s upload and retention terms deserve attention. Review Stellar’s current privacy terms and your organization’s requirements. A successful conversion does not verify a provider’s internal access controls or deletion practices. Desktop conversion offers a different processing route, but “desktop” alone should not be read as a guarantee of zero network activity.
My recommendation
Start with the mailbox you actually need to recover. Use the preview to check for the folders and messages that matter, confirm the exact edition’s export rights, then validate the resulting PST before replacing any part of your workflow. Stellar’s preview and selective-export approach make that a more informed decision than buying solely on a feature list.
For related tasks, see our Microsoft 365 migration checklist, secure data-transfer guide and EaseUS Data Recovery Wizard review. File recovery and mailbox conversion solve different problems; choose the tool for the data you still have.
Frequently asked questions
Is Stellar’s online converter local to my browser?
No. You access it through a browser, but the workflow uploads your OST to the service. Get authorization before uploading work or confidential mail.
What did the hands-on test cover?
The online walkthrough used a 286 MB OST file. Desktop evaluation covered locating the OST, previewing mailbox contents and selecting folders.
Should I buy before checking the mailbox preview?
Use the available preview first, confirm that the folders you need are present and check the selected edition’s export rights before paying.
How this was evaluated
Hands-on use of the online converter with a 286 MB OST file, plus the Windows desktop application’s file selection, mailbox preview and selective folder export.
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