Univik OST to PST Converter

Excellent TrustRating 4.8 | 1,850 reviews

Convert OST to PST Without Outlook

Univik OST to PST Converter is a fast, secure OST to PST converter that converts Outlook OST files to PST without Outlook installed. Convert single or batch OST files from Exchange and Office 365 with 100% data integrity, folders, attachments and metadata fully preserved.

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  • Convert OST to PST with no Outlook and no Exchange profile needed.
  • Batch convert multiple OST files at once to save hours.
  • Works with Exchange, Office 365 and IMAP OST files.
  • Keeps folder structure, attachments and read or unread status intact.

*Free trial previews all data and converts a limited number of items per folder. Upgrade for unlimited OST to PST conversion.

Univik OST to PST Converter Box

CIO Choice Award

Virus Total Safe

Download with Confidence: Certified Clean by 70+ Antivirus Engines

No Outlook Needed
Batch Conversion
Exchange & Office 365
100% Data Integrity
Offline & Private

Features

Powerful Conversion Features

Everything you need to convert OST files to Outlook PST accurately, in bulk and without data loss.

Convert OST to PST

Convert any OST file to Outlook PST format that opens directly in Outlook. The output is a clean, importable Unicode PST with all items in place.

Convert OST to PST Without Outlook

No Outlook installation, Exchange server or original profile is needed. The converter reads the OST directly, perfect for orphaned and inaccessible files.

Batch OST to PST Conversion

Add a whole folder of OST files and convert them to PST in one run. Ideal for help desks and admins handling many mailboxes at once.

Exchange & Office 365 OST

Converts OST files from Microsoft Exchange, Office 365 and IMAP accounts, including cached mode files, to standard Outlook PST.

Preserves Folder Structure

Inbox, Sent, Drafts, Deleted Items and every custom folder keep their exact hierarchy and names in the converted PST.

Attachments & Metadata Intact

Every attachment, inline image and email property such as to, from, cc, subject and date is preserved, with read and unread status maintained.

Convert Contacts, Calendars & Tasks

More than email. Contacts, calendar entries, tasks, notes and journals are all converted into the PST so nothing is left behind.

Split Large PST Files

Set a split size to break a large OST into smaller PST files. This keeps each PST within safe limits and quick to open in Outlook.

Date Range & Folder Filters

Convert only the mail you need. Filter by date range or select specific folders so the PST contains just the relevant items.

Recover Orphaned OST Files

Convert OST files left behind by deleted mailboxes, closed accounts or crashed Exchange servers, even when Outlook can no longer open them.

All Outlook Versions

Output PST files work with Outlook 2021, 2019, 2016, 2013, 2010, 2007 and Microsoft 365, both 32-bit and 64-bit.

Offline & Secure

A desktop application that works fully offline. Your OST files are processed locally and never uploaded, keeping sensitive mail private.

Data Integrity

Everything is Preserved

OST to PST conversion keeps your mailbox exactly as it was, with nothing lost or changed.

All emails & folders
Attachments & inline images
Contacts & calendars
Tasks, notes & journals
Read & unread status
Email headers & metadata
Folder hierarchy & names
Unicode & non-English text

Simple Process

How to Convert OST to PST in 3 Steps

No technical knowledge and no Outlook required. Convert OST files to PST on Windows 11, 10, 8 and 7 in minutes.

1

Add OST Files

Click Add File or Add Folder to load one OST file or many at once. Drag and drop is supported and no Outlook profile is needed.

2

Preview & Select

Preview the mailbox folders and emails, then apply optional date range or folder filters so you convert only what you need.

3

Convert to PST

Choose PST as the output, set a split size if you want, click Convert and open the new PST file directly in Outlook.

No Outlook Required

Univik Converter vs Manual Outlook Export

See why a dedicated converter beats the manual Outlook export, especially for orphaned and Exchange OST files.

Univik OST to PST Converter

  • No Outlook needed: reads the OST file directly on any Windows PC.
  • Handles orphaned OST: converts files from deleted mailboxes and closed accounts.
  • Batch mode: convert many OST files in a single run.
  • Safe: the original OST is never modified, only read.
  • Full control: filter by date or folder and split large PST files.

Manual Outlook Export

  • Outlook required: needs Outlook installed and the original profile.
  • Fails for orphaned OST: will not work if the mailbox or profile is gone.
  • One at a time: no way to export many OST files together.
  • Time consuming: manual steps repeated for every mailbox.
  • Error prone: a broken profile or sync issue can stop the export.

Use Cases

Common Conversion Scenarios

Mailbox Migration

Migrate OST to PST to move mailboxes to a new server, domain or computer, with the data in portable PST files.

Deleted or Closed Accounts

Recover mail from an Exchange or Office 365 account that no longer exists by converting its orphaned OST to PST.

Offline Backup

Create a portable PST backup of your mailbox that you can store, archive or open on any Outlook installation.

Outlook Cannot Open OST

When Outlook reports a damaged or inaccessible OST, convert it to a clean PST you can load without errors.

Legal & Compliance

Produce standalone PST files for eDiscovery, audits and record keeping without touching the live server.

Bulk Help Desk Tasks

Convert many user OST files in one batch when onboarding, offboarding or consolidating mailboxes.

Specifications

System Requirements

Operating SystemWindows 11, 10, 8.1, 8, 7 (32-bit and 64-bit)
Processor1 GHz or faster
RAM2 GB minimum (4 GB recommended for large OST files)
Disk Space100 MB for installation, plus space for output PST files
.NET Framework4.8 or higher
OutlookNot required for conversion. Needed only to open the output PST
Supported OutputOutlook PST (Unicode), compatible with Outlook 2007 to 2021 and Microsoft 365

Customer Reviews

What Users Say

Excellent, rated 4.8 out of 5 from 1,850 reviews.

DR

Daniel R.

IT Administrator

"We had hundreds of orphaned OST files from a decommissioned Exchange server. This converted every one to PST without Outlook and kept the full folder structure. A real lifesaver for the migration."

★★★★★

PS

Priya S.

System Engineer

"Simple and fast. I converted a 12GB Office 365 cached OST to PST and opened it straight in Outlook. Attachments and read or unread status were all preserved."

★★★★★

MT

Mark T.

Help Desk Lead

"Tried the free trial first, then bought the full version. Batch conversion of multiple OST files at once saved our help desk hours every week."

★★★★★

Overview

The Complete OST to PST Solution

An OST file is locked to one Outlook profile and mailbox, so when that account is gone the data is stranded. Here is the problem and how Univik fixes it.

The Challenge with OST Files

An OST file is tied to a single Outlook profile and Exchange mailbox, so it cannot be opened on another computer or after the mailbox is removed.

  • Outlook has no built-in OST to PST converter.
  • The manual export needs Outlook and the original working profile.
  • Orphaned, inaccessible and Exchange OST files cannot be exported at all.

How Univik Solves It

Univik reads the OST directly and writes a portable PST you can open in any copy of Outlook, with no Outlook, Exchange server or original mailbox needed.

  • Recover and migrate mail from closed or deleted accounts.
  • Works fully offline on any Windows PC.
  • Keeps every email, attachment, contact, calendar and folder intact.

Why Convert

Why Convert OST to PST?

An OST file is locked to the Outlook profile and mailbox that created it, so it is not portable and cannot be opened on its own. Converting it to a PST gives you a portable Outlook data file you can open or import on any computer, even after the original account is gone. For a full explanation of the format, see our guide to the OST file.

This matters most for orphaned OST files. If the mailbox is deleted, the account is removed or the Exchange server goes offline, the OST becomes unreadable. Conversion to PST is the safe, lasting way to recover and keep that mail.

What changes when you convert OST to PST:

AspectOST FilePST File
PortabilityLocked to one profile and mailboxFully portable across computers
Open in OutlookCannot be opened or imported directlyOpens or imports directly
Typical useOffline synced copy of a live mailboxBackup, archive and mailbox migration
If account is goneBecomes orphaned and unreadableStill opens normally

Help Desk

Frequently Asked Questions

Common questions about converting OST files to Outlook PST with Univik.

An OST to PST converter is a tool that reads Outlook OST files and saves their emails, contacts, calendars and attachments into Outlook PST format. Univik OST to PST Converter does this without needing Outlook or the original Exchange profile, so you can open the data on any computer.

Yes. Univik reads the OST file directly and writes a PST file, so you do not need Outlook installed or the original mailbox profile. This is useful for orphaned, inaccessible or Exchange OST files that Outlook can no longer open.

Download and install Univik OST to PST Converter, click Add File or Add Folder to load your OST files, preview the folders, choose PST as the output and click Convert. The new PST opens directly in Outlook.

Yes. It converts OST files created by Microsoft Exchange, Office 365 and IMAP accounts, including cached mode OST files, to Outlook PST with the folder hierarchy intact.

Yes. The converter preserves the full folder structure, all attachments, inline images, read and unread status and email metadata such as to, from, cc, subject and date.

Yes. Batch mode lets you add a whole folder of OST files and convert them to PST in a single operation, with each source kept separate in the output.

The PST files work with Outlook 2021, 2019, 2016, 2013, 2010, 2007 and Microsoft 365, in both 32-bit and 64-bit. The software runs on Windows 11, 10, 8.1, 8 and 7.

A free trial lets you preview all OST data and convert a limited number of items per folder so you can confirm the results. The full version removes the limit for unlimited OST to PST conversion.

Yes. You can set a split size so a large OST is exported into smaller PST files, which keeps each PST within safe size limits and easy to open in Outlook.

An OST is locked to its original profile and mailbox, so it is not portable and cannot be opened if that account is gone. Converting to PST gives you a portable file you can open or import in any Outlook, which is essential for backups, migration and recovery.

Outlook can open and import PST files but not standalone OST files. An OST is locked to the profile and mailbox that created it, so if that account or Exchange server is gone the OST is orphaned. Converting it to PST lets you open the data in any version of Outlook.

Related Tools

More Univik Converters

OST Converter (All Formats) Convert OST to PST, EML, MSG, PDF and more from one tool.
OST Viewer Open and read OST files without converting them.
What Is an OST File? Full guide to the OST file format and structure.

Ready to Convert OST to PST?

Download the free trial and convert your OST files to Outlook PST today, no Outlook needed.

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Windows 11/10/8/7