OST to PST Converter
Fast, Lossless & 100% Offline
Extract and recover emails, attachments, contacts, and calendars from orphaned, corrupted, or inaccessible Outlook OST files. Converts directly to healthy PST, EML, MSG, and MBOX files without requiring Exchange Server or Outlook installation.
Conversion Highlights
No Outlook or Exchange Needed
Converts orphaned and disconnected OST files directly without requiring active user accounts or servers.
Maintains Complete Folder Hierarchy
Preserves original Inbox, Sent Items, sub-folders, custom flags, and unread statuses 1:1.
Handles 50 GB+ Large OST Files
Advanced 64-bit multi-threaded parser processes massive mailboxes with built-in PST splitting options.
Recovers Contacts, Calendars & Tasks
Complete recovery of meeting requests, recurring events, vCards, address books, and notes.
Industry-Leading Performance
Why IT Pros Rely on WindowsUtils OST to PST Converter
Engineered for rapid mailbox recovery during Active Directory crashes, employee offboarding, and Exchange migrations.
Extract Inaccessible OST Files
When Outlook displays 'Cannot open your default e-mail folders', our direct MAPI parser recovers inaccessible mail data without needing the original user profile.
100% Offline Data Privacy
Unlike online converter websites that force you to upload company secrets to remote servers, our software executes strictly offline on your Windows desktop.
Multiple Output Formats
Convert OST directly to Microsoft Outlook PST, or export individual messages to standard EML, MSG, MBOX, and searchable PDF with embedded attachments.
Free Pre-Conversion Preview
The built-in tree viewer lets you inspect all emails, sender headers, HTML bodies, contacts, and calendar entries before converting a single byte.
Automatic PST File Splitting
Avoid Outlook 50GB file performance bottlenecks by splitting output PST files by custom size limits (e.g., 5GB, 10GB, 20GB) automatically during export.
Granular Date & Folder Filters
Export only recent emails from specific tax years or project timeframes using advanced date-range and folder exclusions to reduce storage footprints.
Comparative Analysis
WindowsUtils vs Microsoft SCANPST vs Online Converters
Evaluate why dedicated desktop conversion outperforms native repair scripts and risky cloud upload portals.
| Feature / Capability | WindowsUtils OST to PST | Microsoft SCANPST.EXE | Online Cloud Converters |
|---|---|---|---|
| Recovers Orphaned Disconnected OST | ✓ Yes (100% Standalone) | ✗ No (Requires Exchange SID) | Partial (Fails on corrupted items) |
| Data Privacy & GDPR Security | ✓ 100% Local PC Processing | ✓ Local | ✗ Uploads confidential emails to web |
| File Size Capacity | 50 GB+ with Auto-Split | Fails/Crashes above 2 GB | Hard caps (e.g. 50 MB – 250 MB) |
| Outlook Installation Required? | ✓ No (Standalone Engine) | ✗ Yes (Mandatory) | ✓ No |
| Extraction of Contacts, Calendars & Tasks | ✓ Complete MAPI Extraction | ✗ Frequently drops contacts | Emails only (Most drop calendars) |
| Pricing Model | $49 (One-Time Lifetime) | Free (Built-in) | $10 – $30 per single file |
Compatibility & System Specs
Engineered for Enterprise & Home Systems
- • Windows 11 (64-bit)
- • Windows 10 (32-bit & 64-bit)
- • Windows 8.1, 8, 7
- • Windows Server 2022, 2019, 2016
- • Microsoft 365 (Office 365)
- • Outlook 2024, 2021, 2019
- • Outlook 2016, 2013, 2010, 2007
- • Exchange Server 2019, 2016, 2013
- • Microsoft Outlook PST (Unicode)
- • EML (Windows Mail, Thunderbird)
- • MSG (Individual Outlook message)
- • MBOX, PDF, HTML, RTF
Common Questions
Frequently Asked Questions About OST to PST Conversion
How do I convert OST to PST without Outlook installed?
WindowsUtils OST to PST Converter is a completely standalone application that directly parses raw MAPI database blocks from your .ost file. It does not require Microsoft Outlook, Exchange Server, or an active Internet connection to perform the conversion.
Can this tool recover orphaned or inaccessible OST files?
Yes. Even if your Exchange mailbox is deleted, the employee has left the company, or the profile is damaged, the software bypasses Exchange SID authentication and restores all emails, contacts, calendars, and attachments.
Is there a maximum file size limit for OST conversion?
No. The 64-bit processing engine effortlessly processes massive OST files exceeding 50 GB. It also includes an automatic PST file splitter to segment large outputs into standard 10 GB or 20 GB archives.
Why should I use offline software instead of an online OST to PST converter?
Online converters require uploading multi-gigabyte proprietary email mailboxes over the internet to third-party cloud servers, violating GDPR, HIPAA, and data confidentiality. Our offline desktop tool processes 100% of your data locally on your Windows PC.
What items are extracted during the conversion process?
The software extracts complete email folders (Inbox, Sent, Drafts, Archive, Custom Folders), attachments (PDFs, docs, images), contacts, address books, calendar appointments, tasks, and notes with original timestamps and metadata intact.
Recover Your Inaccessible OST Mailbox in Minutes
Download the free trial to scan and preview all your emails, contacts, calendars, and attachments instantly.