If you are using a Microsoft Exchange Server account, all your email messages and other mailbox items such as: calendar, contacts, tasks, notes, etc. can be delivered to and stored on the server. A local copy of these items can be stored on your computer system in an Outlook data file known as OST (Offline Storage Table). It is an offline Outlook data file that allows users to work offline or work with their mailbox data even if they are not connected to Exchange Server. Because of this feature, the file is called Offline Outlook Data File. It is automatically synchronized with the Exchange computer when the connection to MS Exchange Server becomes available.
An offline Outlook data file is considered a beneficial file format for Outlook users; on the other hand, it also has some negative points. Like a PST file, it also has some limitations that can lead to serious problems. Similarly, since an Outlook PST file has size limitation, an offline Outlook data file also has size limitation problem. If the file exceeds the maximum size, it may get corrupted or damaged. This is not the only cause of corruption; in fact, there are several reasons that can cause corruption such as: virus attacks, hard drive failure, unexpected MS Outlook cancellation, network failure, system power failure, sync error, etc.
If exceeding the size of an OST file is the main problem, it can be solved by configuring a sync filter in your Exchange Server mailbox folders. This manual technique helps you reduce the file size without causing any side effects. The following steps are required to perform this technique:
- Right-click on the mailbox folder you want to shrink > click on Properties.
- The Properties dialog box appears. click on Synchronization tab > Filter button.
- The Filter dialog box appears. Now choose the default for synchronization (set the desired filters).
- click on Okay. Now restart your MS Outlook program.
If you suspect corruption in your offline Outlook data files, you can perform an integrity check with SCANOST.EXE. This is very similar to SCANPST.EXE and performs actions in the same way as SCANPST.EXE. It is used to scan corrupt OST files and determine the errors in OST files. If the selected OST file is found corrupted, the file structure is automatically reset and headers rebuilt.
SCANOST.EXE can be found in these locations based on your MS Office version:
- For 2010: C: Program Files Microsoft Office Office14
- For 2007: C: Program Files Microsoft Office Office12
- Before 2003: C: Program Files Common Files System MSMAPI scanost.exe
- For 2002 / XP: C: Program Files Common Files System MAPI scanost.exe
- Before 2000: C: Program Files Common Files SystemMAPI NT scanost.exe
Before using this utility, make sure that your MS Outlook program is not running on your system, it must be shut down. Go to the location shown above according to your MS Outlook program and follow the steps below:
- Find you SCANOST.EXE and double click on it.
- The Microsoft Outlook Inbox Repair Tool window will appear on your screen.
- Now select the profile that contains the corrupt OST file.
- Select the correct option. Check the box “Correct mistakes” to solve the problems.
- click on Start scanning to scan the selected OST file.
- After the file is scanned and repaired, you will receive a message that OST has been repaired.
Unfortunately, SCANOST.EXE can sometimes fail to fix corrupt OST files. In such situation, you need third party OST Recovery software that can fix your corrupt OST file and recover your data from it. Since you have no other better option than this one, you should check this out. It helps you scan corrupt OST files and fix any level of corruption. Usually, third-party recovery tools are available with a free demo or trial version. You can check them before buying the full version. With the demo or trial version, you can preview recovered data and examine the software.