Stellar Converter for OST – OST to PST, Mailbox Migration, Email Export

What is included in Stellar Converter for OST?

OST Conversion – Converts inaccessible, orphaned, encrypted, and IMAP OST files.
Complete Mailbox – Extracts emails, attachments, contacts, calendars, notes, tasks.
Multiple Formats – Saves to PST, MSG, EML, RTF, PDF, HTML.
Mailbox Preview – Preview every item before you save.
Performance Metric – Converts OST files with no size limit.
Important – Windows-only software; macOS is not supported.

What are the main benefits of Stellar Converter for OST?

Stellar Converter for OST is a Windows utility that pulls mailbox data out of inaccessible, orphaned, or encrypted Outlook OST files and rebuilds it as an importable PST. It is built for the moment Outlook will not open or the original Exchange or Microsoft 365 mailbox no longer exists.

No Exchange – Works without a live Exchange account or profile.
Data Integrity – Keeps folder hierarchy, metadata, and read status.
Verify First – Preview mailbox items before committing the save.
Flexible Output – Save single threads as PDF or MSG.
Bulk Migration – Technician converts many OST files together.
Direct Export – Technician pushes data into Microsoft 365.

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For more background on backup planning, read our guide:

What does Stellar Converter for OST do?

Stellar Converter for OST extracts the contents of an Outlook OST file and rebuilds them as a PST you can import back into Outlook, without needing the original Exchange connection or profile. Because an OST is locked to the profile and MAPIEntryID that created it, a deleted mailbox normally makes the file unreadable, and the converter reads it directly instead. It recovers emails, attachments, contacts, calendars, tasks, notes, and journals, including items from Deleted Items folders. Before saving, it shows a full three-pane preview so you can confirm the data is intact.

Who is Stellar Converter for OST best suited for?

It is aimed at IT admins and Outlook users who lost access to mailbox data after a profile was deleted, an Exchange server was decommissioned, or a Microsoft 365 migration left an orphaned OST behind. In those cases Outlook cannot reopen the file and there is no account to re-sync from, so the cached OST is the only remaining copy of the mail. The tool turns that stranded OST into a portable PST that opens on any machine running Outlook. For technicians handling several mailboxes at once, the Technician edition adds batch conversion of multiple OST files in a single pass.

What is the difference between the Corporate, Technician, and Toolkit editions?

All three editions perform the core OST-to-PST conversion and can save data to PST, MSG, EML, RTF, PDF, and HTML. Corporate is the single-machine option for straightforward conversion. Technician adds batch conversion of multiple OST files, compacting and splitting of large PST output, and direct export to Microsoft 365 and live Exchange. Toolkit includes everything in Technician plus extra Outlook tools such as PST repair and PST merge. The table below shows which capabilities sit in each edition.

Which file types and Outlook items can it convert?

Converted mailbox data can be saved as PST, MSG, EML, RTF, PDF, or HTML, so a single recovered thread can be handed over as a readable PDF instead of a full mailbox. From the OST it extracts emails, attachments, contacts, calendar entries, tasks, notes, and journals, and it can also recover items sitting in Deleted Items. Encrypted or password-protected OST files are supported, which matters because every OST is sealed with a profile-specific key. Date-range, folder, and sender filters let you convert only the mail you actually need rather than the whole file.

What are the main limitations of Stellar Converter for OST?

It runs on Windows only; there is no native macOS build, so Mac users need a Windows machine to convert an OST. The Corporate edition handles conversion but does not include batch processing, PST compacting or splitting, or direct Microsoft 365 export, all of which require the Technician edition. Repairing a corrupt PST or merging PST files is not part of the converter itself and is only available in the Toolkit bundle. The free demo previews mailbox content but saves a maximum of 20 items per folder, so a paid edition is needed for a full export.

What should you check before choosing Stellar Converter for OST?

Match the edition to the job: Corporate for a one-off OST-to-PST conversion on a single PC, Technician if you need batch conversion, PST splitting, or migration into Microsoft 365, and Toolkit if you also want PST repair and merge tools. Confirm you are working on Windows, since the tool will not run on macOS. Run the free demo first, because it previews your OST and proves the file is readable before you buy, which is useful when an OST is orphaned or partly corrupt. If the OST is very large, plan for the Technician edition so oversized PST output can be split automatically and avoid file corruption.

Frequently asked questions about Stellar Converter for OST

Will the converted PST open directly in Outlook?

Yes. The output is a standard PST that you add through Outlook's Open & Export option, with the original folder tree and metadata preserved. No Exchange reconnection is required once the PST has been created.

Does it convert OST files from older Outlook versions?

Yes. It converts OST files created in current and earlier Outlook releases, including Outlook 2021, 2019, 2016, and 2013. The file is read directly, so the Outlook version that generated the OST does not need to be installed to recover its data.