Offline Storage Table (OST), also referred to as Offline Folder, is an Outlook data file that stores a synchronized copy of all your mail items from live Exchange Server, Office 365, IMAP, or Outlook.com on the local machine. As you send or receive emails, the file may get large or exceeds the maximum recommended limit (~20-25 GB). This can lead to inconsistencies in the OST file, resulting in Outlook performance issues and errors.
Further, events such as system crashes, abrupt shutdown, force close Outlook, virus or malware intrusion, faulty add-ins, etc., can also cause damage to the OST file.
OST file becomes orphaned when the email profile is deleted from the online mailbox server. Since OST is encrypted by default with MAPIEntryID GUID key, an orphaned OST cannot be opened or accessed in the same or any other Outlook profile.
In such scenarios, an OST to PST converter software comes in handy and helps restore the mail items from inconsistent, inaccessible, and orphaned OST files. Below we have listed the top 5 OST to PST converter software with their pros and cons to help you choose the best one based on your needs.
Stellar Converter for OST
Stellar Converter for OST is the most popular and reliable OST to PST converter software to extract mail items from inaccessible, encrypted, or orphaned OST files and save them to Outlook importable PST format. The OST to PST converter software also allows you to save the mail items in other common file formats, such as EML, MSG, PDF, RTF, and HTML.
Further, you can save the mail items directly to an existing Outlook profile on the system or export them to Office 365 and live Exchange Server with complete integrity. The software maintains the folder structure and hierarchy while converting or exporting the file items to desired format or destination server.
Stellar Converter for OST is available in two editions: Corporate and Technician. Below are the features of Stellar Converter for OST based on the edition you choose:
- Converts OST into PST format without file size limit.
- Converts all mail items with complete integrity and precision.
- Preview the mail items, including attachments, in a three-pane window.
- Extracts mail items from encrypted OST files to PST.
- Maintains the hierarchy of the folder and data integrity.
- Saves the mail items in PST, HTML, PDF, EML, MSG, and RTF formats.
- Supports Outlook 2000, 2002, 2003, 2007, 2010, 2013, 2016, 2019, and 2021.
It includes all the features of the Corporate edition plus the following:
- Batch conversion to convert multiple OST files into PST simultaneously.
- Compacts large or oversized PST files to reduce the resultant PST file size.
- Splits large PST files into smaller PSTs based on date, size, mail id, and folder.
- Exports to existing Outlook profile.
- Exports to live Exchange Server.
- Exports to Office 365.
- Exports Outlook contacts to CSV format.
Stellar also provides a Toolkit edition which is a software suite that consists of Stellar Converter for OST – Technician edition along with utilities to repair corrupt PST files, merge small PST files, split large PST files, de-duplicate the emails in Outlook, compact oversized PST files, recover Outlook password and deleted mail items from Outlook.
- The free version scans, converts, and previews mail items from the OST file but require activation to save the mail items.
SysTools OST to PST Converter
SysTools OST to PST converter is a reliable OST converter software to convert inaccessible or orphaned OST files of Outlook 2019, 2016, 2013, 2010, and below versions into PST format. The software can convert single or multiple OST files simultaneously into PST format. It can also convert encrypted OST files with precision. Besides PST, you can also convert and save OST mailbox data in common file formats, such as EML, MSG, HTML, or export directly to Office 365.
- Converts OST files into PST with precision.
- Saves converted mail items in EML, MSG, HTML, and PDF formats.
- Previews mail items after conversion.
- Supports inaccessible and orphaned OST files.
- Converts OST files without file size limit.
- Converts multiple OSTs into PSTs with the Batch Conversion option.
- Decrypts protected Outlook OST files by removing S/MIME and OpenPGP encryption.
- Supports Outlook 2003 and later versions.
- Compatible with Windows 11, 10, 8.1, 8, and 7
- It requires Microsoft .NET Framework 4.5 or later. Otherwise, you may encounter compatibility issues.
- There is no option to compact or split large mailboxes or PST files after conversion.
Offline OST to PST Converter
Offline OST to PST Converter is also a powerful OST to PST converter software available for Windows computers. Users and administrators can use the software to convert their inaccessible or orphaned Outlook OST files into PST or other common formats, such as MSG, EML, VCF, or TXT. It recovers and restores all emails, tasks, journals, items, notes, contacts, events, calendars, etc., from OST to an Outlook importable PST file.
- Converts inaccessible and orphaned OST into PST format.
- Supports password-protected OST files.
- Converts OST files of any size without any limit.
- Maintains folder hierarchy.
- Previews extracted mail items after scanning the OST file for precise conversion.
- Supports ANSI (Outlook 97-2003) and UNICODE (Outlook 2007 and later) OST files.
- Recovers mail items from corrupt or damaged OST files.
- It cannot compact or split large OST files into smaller PST(s).
- The OST conversion is a bit slow.
- Does not export OST to Office 365 or live Exchange.
- Cannot convert multiple OST files at once.
Kernel for OST to PST Converter
Kernel for OST to PST Converter is an advanced OST converter software for Windows to convert inaccessible, encrypted, or orphaned OST files into PST format. The software helps Outlook users and Exchange administrators retrieve user mailboxes from local orphaned or inaccessible OST files and restore them to their original or new mailboxes or different Outlook profiles.
- Converts Outlook OST files into PST with complete accuracy.
- Recovers and restores lost or deleted mail items from OST files.
- Exports mail items from OST to Gmail/Outlook.com accounts.
- Retains original folder structure.
- Provides advanced filters to refine mail items before saving based on item type, date range, folder name, etc.
- Generates a detailed HTML graphical report after converting OST into PST for later analysis.
- The free version offers limited options. Requires license to unlock features and save options.
- There is no option to compact or split large OST files into smaller PSTs.
Shoviv OST to PST Converter
Shoviv OST to PST Converter converts inaccessible or orphaned OST files and recovers damaged or corrupt OST files to PST format. In addition, the software supports other saving options, such as HTML, EML, vCal, and vCard formats. You can also use the software to recover lost or permanently deleted mail items from OST files and save them as PST or export them directly to an Office 365 mailbox. In addition, you can convert OST files of any size and split the large OST file into smaller PSTs.
- Quickly converts inaccessible or orphaned OST files into PST format.
- Recovers permanently deleted mail items from OST files.
- Converts single or multiple OST files.
- No OST file size limit for conversion.
- Previews mail items extracted from OST file.
- Maintains the hierarchy of the folders and data integrity.
- Supports all Outlook versions.
- Advanced search options to locate and save specific mail items.
- Supports multiple saving options, such as HTML, EML, vCal, vCard, MSG, etc.
- Exports mail items directly to Office 365 mailbox.
- Splits large PST files while saving to avoid corruption.
- Does not support Office 2021 version.
- Cannot convert encrypted or protected OST files.
- It does not highlight or distinguish the deleted items for saving.
The five best OST to PST converter tools discussed in this post is available for Windows. Users, whether professionals or administrators, can use them to convert and export mail items from inaccessible, encrypted, or orphaned OST files to Outlook importable PST. They can also export the individual or multiple mail items to other formats, such as HTML, EML, MSG, PDF, and RTF, with complete integrity and precision. Some advanced OST to PST converter software allows you to export mail items from OST files to a mailbox on Office 365 or live Exchange Server.