🏆 Excellent ★★★★★ TrustRating 4.8 (3,892 reviews)

OST File Converter

Convert Outlook OST files to PST, PDF, EML, MSG and 15+ formats. Open orphaned OST files without Exchange Server connection.

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  • Convert orphaned OST files without Exchange Server connection
  • Export to 15+ formats including PST, PDF, EML, MSG, MBOX
  • No Outlook required - works as standalone converter
  • Complete data recovery - emails, contacts, calendars, tasks
  • 100% offline processing, your data never leaves your computer

Version 6.0 | 18 MB | Windows 7/8/10/11 | Free version converts limited items

OST File Converter
Inbox
Sent Items
Contacts
Calendar
Export to PST

Export Formats

Convert OST to Any Format

Export your Outlook OST emails to 15+ popular file formats

PST
Outlook PST

Portable Storage

PDF
PDF

Adobe Documents

EML
EML

Standard Email

MSG
MSG

Outlook Message

MBOX
MBOX

Thunderbird

HTML
HTML

Web Pages

Also supports: TXT, DOC, DOCX, RTF, XPS, MHT, CSV, VCF (Contacts), ICS (Calendar), and more.

Quick Summary

What is OST File Converter?

OST (Offline Storage Table) is Outlook's offline cache file that stores a synchronized copy of your mailbox from Exchange Server, Office 365, or IMAP accounts. Unlike PST files, OST files are encrypted and tied to a specific Outlook profile.

The problem with OST files is that they become "orphaned" when you lose access to the original Exchange account - whether due to leaving a company, Exchange server decommissioning, profile corruption, or computer change.

The 4n6 OST Converter can open these orphaned OST files and convert them to portable formats like PST, PDF, EML, or MBOX - recovering your emails, contacts, calendars, and other data without needing the original Exchange connection.

This is essential for data recovery, email migration, legal discovery, and backup purposes.

Quick Facts
  • ✓ Free Version Available
  • ✓ 15+ Export Formats
  • ✓ Orphaned OST Support
  • ✓ No Exchange Required
  • ✓ No Outlook Required
  • ✓ Encrypted OST Support
  • ✓ Batch Processing
  • ✓ 100% Offline

When You Need It

Common OST Conversion Scenarios

Situations where OST to PST conversion becomes essential

🔗
Orphaned OST

Lost Exchange connection

⚠️
Corrupted Profile

Outlook won't open

🔄
Job Change

Left company, need data

💾
Data Backup

Create portable backup

🔧
Data Recovery

Recover from old PC

📁
Email Archive

Long-term storage

Common Challenges

Why You Need to Convert OST Files

🔗
Orphaned OST Files

Lost connection to Exchange Server? OST files become inaccessible when the original account is deleted or unavailable.

✓ Convert orphaned OST to portable PST format

🏢
Left Your Company

Changed jobs but need access to your old work emails? Your OST file contains all your mailbox data.

✓ Extract emails before losing access forever

🖥️
Computer Change

Got a new computer but can't open your old OST file? OST files are tied to the original profile.

✓ Convert to PST that opens on any computer

⚖️
Legal & eDiscovery

Need to produce Exchange emails for legal proceedings? OST files contain complete mailbox records.

✓ Convert to PDF with metadata for evidence

🔧
Profile Corruption

Outlook profile corrupted and won't open? Your data is still in the OST file.

✓ Recover all data from corrupted profiles

☁️
Office 365 Migration

Migrating from on-premises Exchange to Office 365? Convert OST to PST for clean migration.

✓ Create PST files for cloud migration

File Locations

Where to Find OST Files

📁 Windows 10/11 Default Location
C:\Users\[Username]\AppData\Local\Microsoft\Outlook\

Most common location for OST files in modern Windows versions.

📁 Older Windows Versions
C:\Users\[Username]\Local Settings\Application Data\Microsoft\Outlook\

Location used in Windows XP and older systems.

🔍 Find in Outlook Settings
File → Account Settings → Data Files

Open Outlook and navigate to see the exact location of your OST file.

📝 OST File Naming
[[email protected]].ost or [username].ost

OST files are typically named after the email address or username.

Complete Data Recovery

All OST Data Supported

The OST Converter extracts all Outlook data types from your OST files.

  • ✓ Emails: Inbox, Sent, Drafts, all custom folders
  • ✓ Contacts: Export to VCF or CSV format
  • ✓ Calendars: Export to ICS format
  • ✓ Tasks: To-do items and assignments
  • ✓ Notes: Outlook sticky notes
  • ✓ Journals: Activity logs and entries
OST File Preview
Email Messages
18,456 emails
✓
👤
Contacts
892 contacts
✓
📅
Calendar Events
2,341 events
✓
📎
Attachments
5,678 files
✓
✅
Tasks & Notes
189 items
✓

FAQs

Frequently Asked Questions

OST (Offline Storage Table) is Outlook's offline cache file that stores a synchronized copy of your mailbox from Exchange Server, Office 365, or IMAP accounts. It allows you to work offline and syncs when connected.

Key differences from PST:

  • OST is tied to a specific Outlook profile and cannot be opened elsewhere
  • PST is portable and can be opened on any computer with Outlook
  • OST is encrypted and linked to the Exchange account
  • PST is a standalone file you can share or move
Yes! The 4n6 OST Converter is specifically designed to open and convert orphaned OST files that are no longer connected to Exchange Server. This is useful when you've left a company, the Exchange server has been decommissioned, your profile is corrupted, or you're on a different computer.
OST files are encrypted and tied to a specific Outlook profile. Outlook won't open an OST file if: (1) the original profile is deleted or corrupted, (2) you're on a different computer, (3) the Exchange account no longer exists, or (4) you don't have the original Windows user account. Our converter reads OST files independently.
Yes, the OST Converter supports the standard Outlook encryption used in OST files. It can read encrypted OST files created by all versions of Outlook and convert the contents to your chosen format.
The OST Converter can recover emails from the Deleted Items folder and sometimes from the Recoverable Items folder if they haven't been permanently purged. However, emails that have been hard-deleted and purged may not be recoverable.
The free version lets you preview unlimited OST files with all folders, emails, contacts, and calendars. You can convert a limited number of items per folder to test all export formats. Upgrade to the full version for unlimited conversion without restrictions.

Expert Support

Need Help Converting OST Files?

Our experts are ready to assist with orphaned OST recovery, conversion issues, or technical questions.

Connect with Expert →

Customer Reviews

What Users Say About OST Converter

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