reference = 3511387454, 3886957240, 3711659324, 3661215741, 3889884615, 3512805494, 3511829113, 3485789243, 3888349328, 9517857190, 8003192482, 3888242486, 3792698558, 18005082597, 3884611733, 3513872160, 3277231786, 3533890476, 3711515150, 3895274422, 3395690482, 3204837945, 3715726487, 3510124224, 3512791806, 3455243680, 3277981029, 3275795970, 3533586227, 3509059118, 3385212925, 18003366675, 3669755856, 3207643029, 3511950605, 3716184523, 3509353823, 3534568305, 3509055524, 18448268400, 6513150012, 3270117307, 3534306477, 3792734142, 3714686648, 8668218411, 3339165062, 916787020, 3341573838, 911086273, 3209472687, 3509439362, 3293407935, 7865678310, 3313833928, 3791532282, 983460133, 3483455262, 3274959642, 689358690, 3758072693, 648818828, 3888555987, 3441323478, 3286375616, 3289545628, 3914520720, 621144595, 3510549173, 945236377, 3337749188, 3509145300, 3801262321, 3515170289, 624722151, 3510183424, 3517153450, 18336343155, 650773442, 3517277520, 913276540, 3892844902, 3515641598, 3516811133, 3209198752, 3495649305, 3473232114, 18002627890, 3497048602, 3884064290, 606805661, 919462920, 685072404, 944340856, 678612257, 865863008, 911081011, 912700851, 911938739, 3711080579, 658099420, 3475883230, 919199477, 4378373966, 3205678419, 3715685446, 3509332441, 3509471757, 3533962990, 7243436495, 919611528, 3792872698, 3533803421, 3275454486, 3716998958, 3331284673, 5517119838, 657030769, 3511966093, 494409169, 3516803520, 3408825034, 6014939427, 3509415116, 799600320, 868202718, 3204472632, 3512616862, 3509146710, 919076725, 960396505, 3716382719, 3533281094, 3314435632, 493625848, 5146870250, 3294168931, 490659557, 490701650, 919462564, 921.168.1.1, 491299532, 3513649994, 692264662, 493073099, 900841941, 3663656425, 02.726.264.62, 18335874578, 623483560, 3886916346, 3200164970, 3533181794, 910808002, 3342255175, 3512289591, 192.168.1000.1, 111.93.16.209, 8008277223, 7168849120, 192.168.1001.1, 192.168.1.00.1, keisersmachen, 494568898, 3937911490, 3482713834, 2165581010, 490768936, 3509925968, 3427646875, 490000331, 490254092, 6193332200, 919591531, 490659555, 492172033, 3890484599, 490309134, 492848020, 490062684, 491160122, 490659554, 490575427, 3512356294, 490001513, 490675817, 490734486, 3313508782, 491264336, 3312278770, 492848319, 491440030, 3458726663, 490319577, 3899087037, 490680422, 3338530062, 490000405, 491168210, 3534977890, 491110948, 491338170, 491899823, 2129456248, 491061086, 3483464178, 8935246914625, 8935246903056, 490005295, 491071007, 491551829, 491376009, 491322206, 3510461825, 958873072, 491348949, 7372728667, 637126735, 490020767, 3427655221, 18003275172, 3454616361, 490057054, 493657568, 3297757691, 3509544387, 490740295, 490709191, 490870362, 491349632, 8901544027787, 3510367923, 490750659, 491010673, 7501024513628, 2123310200, 3274926684, 3452158868, 2123540354, 944230045, 7501024595495, 661891603, 917676371, 491173583, 604303824, 490008739,

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Teck Thrive > CRM and Project Management > 4 Best Online OST to PST Converters for Orphaned OST
online-ost-to-pst-converter
Syed Asad
Syed Asad
October 27, 2026
0
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4 Best Online OST to PST Converters for Orphaned OST

You have just changed jobs, and your old laptop still holds an OST file with years of client emails, invoices and contacts. The account behind it was switched off on your last day. Now Outlook refuses to open the file, and the mail you need feels locked away for good.

The good news is that your mailbox data may still be recoverable. An orphaned OST file can often be converted to PST using a converter that reads the file directly, without relying on the original Outlook profile or Exchange account.

However, not every converter offers the same capabilities. Some allow free conversion up to a specific file size, while others let you preview mailbox data before paying. File-size limits, privacy policies, supported OST formats, and pricing also vary.

In this guide, we compare four online OST to PST converters for orphaned OST files, covering their free limits, pricing, supported features, and potential drawbacks to help you choose the right tool.

Before exploring the tools, let’s first understand what an orphaned OST file is, why it becomes inaccessible, and why a dedicated OST to PST converter may be needed to recover its mailbox data.

What Is an Orphaned OST File?

An OST file is the offline copy of a Microsoft 365, Exchange or Outlook.com mailbox that Outlook keeps on your PC. It becomes “orphaned” when the account or profile that created it is gone. Common causes include:

  • Your account was deleted after you left a company.
  • IT reset or removed your Outlook profile.
  • The Exchange server crashed or was decommissioned.
  • You moved to a new PC and only copied the OST file.

Outlook cannot open an orphaned OST, and renaming it to .pst does not work. The Import/Export Wizard is no help either, because it only exports from a working account. That leaves third-party OST to PST converters.

Top 4 Online OST to PST Converter Tools for Orphaned OST

Stellar Online OST Converter

Stellar Online OST Converter is the most complete option on this list, and the best fit for most orphaned OST files. It comes from Stellar, a data recovery company working since 1993, and is built for orphaned and inaccessible OST files from deleted profiles, crashed Exchange servers and failed syncs.

  • Free plan: one OST under 500 MB per session, no credit card.
  • Paid: $39.99 per mailbox for files up to 5 GB; the desktop edition converts five files of any size for $79.
  • Keeps: emails, attachments, contacts, calendars, tasks, notes, journals and folder structure.
  • Extras: browser preview of folders and item count before download, Outlook 2003–2021 OST support, and password-protected OST files.
  • Privacy: SSL upload, fully automated processing, files deleted after 24 hours (Free) or 48 hours (Premium).

The catch: sign-in is required, and only one file converts per session.

OSTtoPST.online

OSTtoPST.online is the pick for very large OST files, because it sets no file size limit. The service is run by File Master LLC in Bulgaria and works from any device, including Mac, Android and iOS.

  • Free: preview of the folder structure, plus a demo PST limited to 5 items.
  • Paid: $10 per GB, charged only after a successful conversion.
  • Size: no stated limit; the provider says it has converted test files of 55 GB, 73 GB and 110 GB.
  • Supports: ANSI and Unicode OST from Outlook 97 to Microsoft 365, plus encrypted and password-protected files.
  • Privacy: AES-256 encrypted upload and GDPR-compliant handling; files are deleted after 10 days.

The catch: pricing per GB makes big mailboxes expensive, and the provider notes its online version does not handle non-English, non-Unicode text.

Recovery Toolbox Online OST to PST Converter

The Recovery Toolbox online converter is the quickest to start, because it needs no registration. It is the online version of the Recovery Toolbox for Outlook desktop program, and is run by File Master LLC, the same company behind OSTtoPST.online.

  • Free: browser preview of the folder tree and a limited demo PST.
  • Paid: $10 per OST file up to 1 GB, paid by PayPal or card after the preview.
  • Size: the provider says it has tested OST files of up to 150 GB.
  • Supports: orphaned, encrypted, password-protected and damaged OST files, including OST files from Gmail, Yahoo and other IMAP accounts.
  • Privacy: SSL connection, GDPR compliance, and files deleted 10 days after upload.

The catch: there is no free full conversion, and for confidential mail the provider itself recommends its offline desktop tool instead.

FreeConverter.app OST to PST Converter

FreeConverter.app is the simplest free online option, and suits users who want a download link sent by email. The service is based in New Delhi and also offers optional upload apps for Windows and Mac.

  • Free: advertised as a free online converter; the page does not list plan limits or prices.
  • Size: the provider claims no size constraints.
  • Supports: ANSI and Unicode OST, password-protected and encrypted files, from 32-bit and 64-bit Outlook.
  • How it works: sign up, upload the OST, choose PST, and receive a download link by email.
  • Privacy: files are deleted from the server after 24 hours.

The catch: an account is required, there is no preview before conversion, and limits are not published, so test with a small OST first.

Quick Comparison of Online OST to PST Converter

Stellar gives the most for free, while OSTtoPST.online and Recovery Toolbox handle the biggest files.

Tool Free option Paid price Max size Preview Files deleted after
Stellar Online OST Converter Full conversion under 500 MB $39.99 per mailbox (up to 5 GB) 5 GB online; no limit on desktop Yes 24–48 hours
OSTtoPST.online Preview + 5-item demo PST $10 per GB No stated limit Yes 10 days
Recovery Toolbox Online Preview + demo PST $10 per file up to 1 GB Tested to 150 GB Yes 10 days
FreeConverter.app Free (limits not published) Not published No stated limit No 24 hours

Prices and limits as listed on each provider’s website in October 2026.

Conclusion:

An orphaned OST file looks like a dead end, but the emails, contacts and calendar entries inside it are almost always recoverable. The right tool simply depends on your file and your budget. Start with Stellar Online OST Converter, which converts it free. For very large mailboxes, OSTtoPST.online and Recovery Toolbox can handle files well beyond 5 GB. FreeConverter.app is worth a try if you want a free link by email, as long as you test it with a small file first.