OST File Extension

OST file icon
Outlook Offline Folder Format
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What is OST file?

OST file format is used by Microsoft Outlook mailing software. The file can contain data such as email messages, tasks, calendar data or contacts. OST files are used as offline mailbox files if applications is not connected to Micr o soft Exchange server. OST format is also known as Offline Folder File (OFF).

OST files applications

OST is a offline folder file that enables user to perform certain tasks without the need of active internet connection – all changes made by the user will be synchr onized with Microsoft Exchange server upon connection. OST file enables creation of contacts, tasks, email messages and other elements while offline. This features is especially useful in places with limited internet access.

Cretion and location of OST files

OST files is created immediately after choosing ‘Use offline folders’ option available in Microsoft Outlook utility. Upon generation, the file is stores on local hard disk drive, not on the mail server. OST file folder path:

Users[user name]AppDataLocalMicrosoftOutlook.

Similarities to PST format

OST format shares many similarites with PST, however the latter stores data on network cli e nt or server other than Exchange server. OST format supports larger file sizes than PST.

Programs which support OST file extension

The following listing features OST-compatible programs. Files with OST suffix can be copied to any mobile device or system platform, but it may not be possible to open them properly on target system.

Programs that support OST file

Updated: 12/26/2019

How to open file with OST extension?

Problems with accessing OST may be due to various reasons. Fortunately, most common problems with OST files can be solved without in-depth IT knowledge, and most importantly, in a matter of minutes. We have prepared a listing of which will help you resolve your problems with OST files.

Step 1. Download and install Microsoft Outlook

The main and most frequent cause precluding users form opening OST files is that no program that can handle OST files is installed on user’s system. The most obvious solution is to download and install Microsoft Outlook or one to the listed programs: Convert OST to PST, Outlook Recovery Toolbox, Advanced Exchange Recovery. On the top of the page a list that contains all programs grouped based on operating systems supported can be found. One of the most risk-free method of downloading software is using links provided by official distributors. Visit Microsoft Outlook website and download the installer.

Step 2. Verify the you have the latest version of Microsoft Outlook

You still cannot access OST files although Microsoft Outlook is installed on your system? Make sure that the software is up to date. Software developers may implement support for more modern file formats in updated versions of their products. The reason that Microsoft Outlook cannot handle files with OST may be that the software is outdated. The most recent version of Microsoft Outlook is backward compatible and can handle file formats supported by older versions of the software.

Step 3. Set the default application to open OST files to Microsoft Outlook

If you have the latest version of Microsoft Outlook installed and the problem persists, select it as the default program to be used to manage OST on your device. The next step should pose no problems. The procedure is straightforward and largely system-independent

The procedure to change the default program in Windows

  • Right-click the OST file and choose Open with option
  • Click Choose another app and then select More apps option
  • Finally select Look for another app on this PC, point to the folder where Microsoft Outlook is installed, check the Always use this app to open OST files box and conform your selection by clicking OK button

The procedure to change the default program in Mac OS

  • By clicking right mouse button on the selected OST file open the file menu and choose Information
  • Open the Open with section by clicking its name
  • From the list choose the appropriate program and confirm by clicking Change for all....
  • A message window should appear informing that This change will be applied to all files with OST extension. By clicking Continue you confirm your selection.

Step 4. Check the OST for errors

If you followed the instructions form the previous steps yet the issue is still not solved, you should verify the OST file in question. Problems with opening the file may arise due to various reasons.

1. The OST may be infected with malware – make sure to scan it with an antivirus tool.

If the file is infected, the malware that resides in the OST file hinders attempts to open it. Immediately scan the file using an antivirus tool or scan the whole system to ensure the whole system is safe. If the OST file is indeed infected follow the instructions below.

2. Ensure the file with OST extension is complete and error-free

If the OST file was sent to you by someone else, ask this person to resend the file to you. The file might have been copied erroneously and the data lost integrity, which precludes from accessing the file. It could happen the the download process of file with OST extension was interrupted and the file data is defective. Download the file again from the same source.

3. Verify whether your account has administrative rights

There is a possibility that the file in question can only be accessed by users with sufficient system privileges. Log in using an administrative account and see If this solves the problem.

4. Check whether your system can handle Microsoft Outlook

The operating systems may note enough free resources to run the application that support OST files. Close all running programs and try opening the OST file.

5. Verify that your operating system and drivers are up to date

Up-to-date system and drivers not only makes your computer more secure, but also may solve problems with Outlook Offline Folder Format file. It is possible that one of the available system or driver updates may solve the problems with OST files affecting older versions of given software.

Conversion of a OST file

File Conversions from OST extension to a different format
File conversions from other format to OST file
Do you want to help?

If you have additional information about the OST file, we will be grateful if you share it with our users. To do this, use the form here and send us your information on OST file.

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