Resolve OST Errors


Resolving “Cannot open your default email folders…..” Error in OST Files

Offline Storage Table (OST) is an offline folder file that may get corrupted due to various reasons such as server crashes, server database corruptions, virus attacks, unexpected system shutdown, power failure, etc. For repairing the corrupt OST file, a user can use the Inbox Repair Tool that scans only the OST file and not the mailbox on MS Exchange server. The Inbox Repair Tool preserves and resets the file structure and rebuilds the headers.

While opening corrupt, damaged or inaccessible MS Outlook OST files, an error messages given below may be generated:


“Cannot open your default email folders. The file xxxx.ost is not an offline folder file.”

Here, ‘xxxx.ost’ is the offline folder file created by Outlook while working with Exchange mailbox offline. Reasons for occurrence of such an error message are:

  • OST file got damaged or corrupted and cannot be recognized by MS outlook.
  • OST file is associated with a mailbox on the Exchange server and MS Outlook cannot access the associated Exchange mailbox or start synchronizing the mailbox with the offline folders in the OST file.

Some of the instances of generation of the above message are:
  • User forgets to set the email account for accessing the Exchange mailbox correctly.
  • Accidental deletion of the email account for the Exchange mailbox.
  • Communication error between Outlook and Exchange Server.
  • Absence of Exchange email account and email account is based on POP3, IMAP, HTTP or mail servers other than Exchange Server. User sets email account as Exchange-based mistakenly.
In order to resolve the above-mentioned error, user must follow the steps given as follows:
  1. Find the OST file causing the error: Find the OST file using the information provided in the error message. A Search function is also available in Widows for searching the OST file.
  2. Rescue the offline data in the OST file: Use Advanced Exchange Recovery for scanning the OST file, recover the data in it, and save them in an Outlook PST file for accessing the mail messages and all other items using MS Outlook easily and efficiently.
  3. Backup the OST file: Make backups of OST files as per security purposes.
  4. Rename or delete the original OST file causing the problem.
  5. Fix the error:
    1. In case Exchange mailbox and email account are still valid, then make sure that the email account settings in MS Outlook are correct, and Outlook can connect to Exchange Server correctly. Start Outlook and send/receive emails on Exchange mailbox such that Outlook will create a new OST file automatically and synchronize its data with the Exchange mailbox.
    2. In case Exchange mailbox or email account doesn’t exist anymore, then the mail profile becomes incorrect, delete that and create a new one as follows:

2.1.Click Start, and then click Control Panel.

2.2.Click Switch to Classic View if user is using Windows XP or higher versions.

2.3.Double-click Mail.

2.4.In the Mail Setup dialog box, click Show Profiles.

2.5.Select one of the incorrect profiles in the list and click Remove to remove it.

2.6.Repeat the above step until all incorrect profiles have been removed.

2.7.Click Add to create a new profile and add email accounts according to their types.

2.8.Start Outlook having problem solved.