What causes the error 'Outlook data file OST cannot be opened'?
The most common cause of the 'Outlook data file OST cannot be opened' error is an orphaned OST file or improper Outlook shutdown. To resolve the problem you must retrieve your mailbox data from the OST file and convert the OST to PST format with a suitable third-party tool like EdbMails.
Here are some of the most common factors that cause this issue:
- Corruption in the OST file: The OST file, which stands for Offline Storage Table, stores a cached copy of your Exchange Server mailbox and is used for offline access to your email, calendar, and other data in Microsoft Outlook. When the OST file becomes corrupt, you may encounter this error.
- OST file orphaning issue: The OST file can become orphaned when Outlook 365 cannot connect to the Exchange server and is no longer able to synchronize your email data with. This problem can occur when the Exchange server crashes due to hardware failure or when it is decommissioned.
- Improper shutdown of Outlook: If Outlook closes unexpectedly due to a sudden system shutdown or termination of Outlook processes, it can fail to update Outlook inbox and folders. As a result, the OST file can become damaged making your emails inaccessible.
- Incompatible version of Outlook: If you are trying to open an OST file that was created with a newer version of Outlook in an older version of the software, you may encounter this error.
- Antivirus or firewall software: Antivirus and firewall software can sometimes interfere with the functioning of Microsoft Outlook, causing the OST file to become inaccessible.
- Outlook profile corruption: Due to a ransomware attack, the profile you are using in Outlook may become corrupt, rendering the OST file inaccessible. In such cases, you may have to rebuild the Outlook profile.
- Locked Outlook OST file: In some cases, the OST file may be locked for use by another conflicting application, preventing Outlook from opening it.