If you are using a Microsoft Exchange Server account, all your email messages and other mailbox items like: calendar, contacts, tasks, notes, etc. are delivered to the server and saved on it. A local copy of these items can be stored on your computer system in an Outlook data file, which is known as OST (offline storage table). It is an offline Outlook data file that enables users to work offline or work with their mailbox data even when they are not connected to Exchange Server. Due to this feature, the file is called Offline Outlook data file. It gets automatically synchronized with the Exchange computer when the connection to MS Exchange Sever becomes available.
An offline Outlook data file is considered a beneficial file format for Outlook users; on the other hand, it has some negative points too. Like a PST file, it also has few limitations which may create some serious problems. As an Outlook PST file has a size-limitation, in the same way, an offline Outlook data file has also a size-limitation problem. If the file exceeds its size limit, it may become corrupted or damaged. This is not the only cause of corruption; in fact there are various reasons which may cause corruption, such as: virus attacks, hard drive failure, unexpected cancellation of MS Outlook, network failure, system power failure, synchronization error, etc.
If exceeding size of an OST file is the main issue, then it can be resolved by configuring a synchronization filter on your Exchange Sever mailbox folders. This manual technique helps you reduce the file size without causing any side-effect. The following steps are required to perform this technique:
- Right-click the mailbox folder that you want to reduce > click on Properties .
- The Properties dialog box appears. Click on Synchronization tab > Filter button.
- The Filter dialog box appears. Now choose the standard for synchronization (set the filters you want).
- Click on OK . Now restart your MS Outlook program.
If you are suspecting corruption in your offline Outlook data files, you may perform an integrity check by using SCANOST.EXE. This is very similar to SCANPST.EXE and performs actions in the same way as SCANPST.EXE does. It is used to scan corrupt OST files and determine the errors in OST files. If the selected OST file is found corrupted, it automatically resets the file structure and rebuilds the headers.
SCANOST.EXE can be found in these locations according to your MS Office version:
- For 2010: C: Program Files Microsoft Office Office14
- For 2007: C: Program Files Microsoft Office Office12
- For 2003: C: Program Files Common Files System MSMAPI scanost.exe
- For 2002 / XP: C: Program Files Common Files System MAPI scanost.exe
- For 2000: C: Program Files Common Files SystemMAPI NT scanost.exe
Before using this utility, make sure your MS Outlook program is not running on your system, it should be closed. Go to the location shown above according to your MS Outlook program and then follow the steps shown below:
- Locate you SCANOST.EXE and double-click it.
- The Microsoft Outlook Inbox Repair Tool window appears on your screen.
- Now select the profile that contains the corrupt OST file.
- Select the appropriate option. Check the box “Repair Errors” to resolve the issues.
- Click on Begin Scan to start scanning selected OST file.
- Once the file is scanned and repaired, you receive a message saying OST repaired successfully.
Unluckily, SCANOST.EXE may fail sometimes to fix corrupt OST files. In such situation, you need third-party OST Recovery software that can repair your corrupt OST file and recover your data from it. As you have no other better option than this, you have to check it. It helps you scan corrupt OST files and fixes any level of corruption from them. Usually, third-party recovery tools are available with free demo or trial version. You can check them before buying the full version. Demo or trial version enables you to see the preview of recovered data and helps you examine the software.