Fix Cannot Open Default Email Folders, The File .ost is Not an Offline Folder File

Samantha Brown | Published: 2017-08-03T07:22:25+05:30 | How To|

One of a unique feature of Microsoft Outlook, due to which, it is most common is its offline mode synchronization. In case, if there is a server failure or breakdown has occurred, then the users always find it simple and easy to work with Outlook offline OST file, which gets synchronized to the Exchange Server once the network is established again. This feature of Outlook OST file proves to be a boon for many users who cannot afford to delay their work due to server issues. However, this problem arises when any user tries to connect to Outlook OST file and face an error that restricts access to the OST file. One such common error is “Cannot open default email folders, the file xxxx.ost is not an offline folder file.” Here xxxx is assumed to be the name of the OST file. Due to this repeated situation, many users get into trouble and look for a reliable solution to get out of it. In this article, we are going to discuss the solution to the problem to the error.

Reason For The Error Cannot open default email folders, the file .ost is not an offline folder file”

A possible reason behind these types of errors is the corruption of the Outlook OST file. The Offline folders are more prone to damage or virus attacks, which make them highly corrupted and results in inaccessibility of OST files. If the OST file is corrupted, it becomes unable to synchronize with the server. Moreover, the file becomes inaccessible in such a way that Outlook also cannot recognize or sync with it. As a result, whenever a user tries to read or open an OST file, Outlook displays an error showing that it cannot open default emails folders, the file xxx.ost is not an offline folder file.

  • Some of the possible reasons that make the OST file damaged:
  • Faulty Disk sectors
  • Abnormal Outlook Termination
  • Network Related Issues
  • Sudden Power Loss

How to fix Cannot open default email folders, the file .ost is not an offline folder file”

Since the corrupted Outlook OST file makes the situation more terrible and impossible to work in an offline mode. An immediate step is required to repair corrupted Outlook OST file so that it can again become useful to work with. The users can go for the below-given approaches to handle such OST file issues:

Approach 1: Run Inbuilt Repair Tool “Scanost.exe”

The first and the foremost technique to repair an Outlook OST file by using an inbuilt Outlook software, Scanost.exe. It is the simplest method to diagnose and repair minor corrupted Outlook files. So, one can choose to repair the corrupted file in the discussed method as well:

1. Browse the tool at the given location: Drive\Program Files\Microsoft Office.
2. Click Browse to select the corrupted Outlook OST file.
3. Click Start and keep an eye on the file scanning process.
4. The scan generates a list of encountered errors, click Repair to handle the issues.
Once the software completes its execution, Outlook is required to be restarted to view the OST file.

Approach 2: Recreation of OST File

The Outlook users can also choose to recreate the Outlook OST files and can also make certain changes in the cache mode of Outlook Offline storage table files. The inaccessible Outlook OST file can be recreated as:

1. Firstly, close MS Outlook.
2. Open Control Panel? click on Mail?Profiles.
3. Select the associated profile name.
4. Select Properties? Email Accounts.
5. Choose the email address and click on Change.
6. Under Advanced Settings, enable: Use Cached Exchange Mode.
7. Click OK to save changes.
A new OST file will be created for the specified email account.

Limitations Of Manual Methods To Fix Cannot open default email folders, the file .ost is not an offline folder file”:

The above-discussed utility might show some error which is there in the Outlook OST file. Sometimes, what happens is that this tool doesn’t find any error but still, users are not able to access the OST file. This is because of the large size of the Offline storage table.

However, sometimes a successfully repaired message is displayed but still, it shows Cannot open default email folders, the file .ost is not an offline folder file”.

Scanost.exe can only repair a .ost file in Outlook if there is a minor damage to the file. Unfortunately, if the damage is major then, it cannot be repaired by this tool. When a user has a need to gain access to the Outlook OST file, a third party tool is the only utility which comes to user’s mind.

Automated Technique to Fix Cannot open default email folders, the file .ost is not an offline folder file”

If the error does not get resolved using the above manual techniques, then the best approach for the users is to go for a Third Party OST file repair tool. This utility offers the following features to deal with all kinds of OST file issues:

  • Capable of viewing all recovered OST file messages.
  • Able to extract & recover deleted messages from OST file.
  • Apply date range filters to export selective items.
  • It maintains email metadata like Reading/Unread status and message dates

Thus, users are advised to go for this software to perform an error free OST recovery. This application instantly scans and repair corrupted OST file and makes it accessible.


Since the most common reason for every OST file related error is corruption, it is always advised to handle these files carefully. Understanding the importance of offline OST file, this article described the solution to overcome OST file errors. A complete manual method has been explained to let the users learn How to fix Outlook OST error message: Cannot open default email folders, the file xxxx.ost is not an offline folder file’.

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