Troubleshoot OST file error: “cannot open your default email folders, the file xxxx.ost is not an offline folder file”

The offline storage table is one of the important MS Outlook data files and used by Exchange Server to allow the users to access their emails and other mailbox items even in the offline mode. User can even create, modify or delete the data in the offline mode, and the relevant changes are then automatically synchronized with the mail server when the internet connectivity is back or available.

The OST files work as the mirror image of exchange database mailboxes available on the user machine, which works when cache exchange mode is enabled. In simpler term, the OST files are an exact replica of exchange mailboxes stored on the host machine.

However, user may sometime face inaccessibility issues by throwing an error message like: ‘cannot open your default email folders, the file xxxx.ost is not an offline folder file’. This error message restrict users to access any mailbox data, no matter how many times they try.

Reasons for the occurrence for this error message:
  1. When offline storage table files (OST) get corrupt or damaged, it is generally not identified by the Outlook and hence MS Outlook does not report about this error
  2. MS Outlook fails to synchronize the offline folders with the associated exchange mailboxes and therefore displays such error.
  3. Communication woes between Exchange Server and Outlook may also result in this error message
  4. Sometimes, virus intrusion or unreliable internet connectivity may be a reason for this error
In such critical cases, the aftermaths of this error message may even lead to information lapse or may affect the complete mailbox data to become inaccessible to open the Outlook mailbox.
Troubleshooting the error message
Follow the Three-method manual technique to resolve this error, but before implementing the methods make sure you have kept the latest and complete backup of the data for safety purpose.
Search OST file and check its file information
  • Find out the specific OST file which is creating trouble and displaying this error message
  • If Outlook is working properly, then try renaming the damaged OST file with a fresh name and then try opening it the MS Outlook application.
  • Make sure that provided user profile information is accurate in Exchange Server as well as MS outlook.
  • Check that stable internet connection persists between Exchange Server and MS Outlook.

METHOD 2 : Identify hardware and software problems
Make sure that there is no software or hardware conflicts that is causing this issue. You may verify that all the available components are working correctly such as data cards, connectors, routers etc. without any interruptions.

Remove and Recreate existing Outlook profile
In this method, this error message has been tried to resolve by deleting the current Outlook profile and replaced by the newly created profile:

Follow the below given steps
  • On the “Start” button, select “Control Panel”.
  • Open “Control Panel” window, double-click on “Mail” option to open it.
  • In “Mail Setup” window, go to the profile section and click “Show Profiles” option to open it.
  • From the available list of profiles, click & choose the profile to be removed.
  • On the General Tab, click “Remove” button to delete the chosen profile.
  • Now, go to “Add” button and click to create and add new profile.
  • Facilitate the account information for that profile and click on “OK”.
  • Lastly, launch the Outlook profile and verify if the problem has eradicated.

However, if the problem still persists, then try using professional third-party recovery software to fix it for you automatically. OST to PST is a reliable OST file recovery tool that restores offline storage files in every corruption condition and enables users to save them in the desired platform like Outlook, Office365, email server or web mail in a single attempt. This OST recovery software embeds advanced algorithms to let you execute flawless conversion of OST files to PST files with utmost safety, speed and convenience.