A Brief glimpse at Outlook OST creation & OST deletion operations:

Outlook OST file is also known as Offline storage table as, it facilitates the working with Outlook data when there is no connection with Exchange or user is in offline mode.

While offline you can work with the OST file as you normally do when connected with Exchange. When the server is connected again, the changes will be automatically updated to the exchange database. This process is called synchronization.

Either only header or full items (header, message body, and attachments etc.) will be synchronized when connection is re- established.

You can use send/receive groups to determine which folders are to be synchronized. You can group Email accounts and folders and set options for them:

• Download header or message.
• Online v/s offline behavior
• Size limit for downloaded messages

Note: You don’t need to set send/receive groups while working Cached Exchange Mode. Only choose folders that you want to be available offline, and then keep those folders synchronized.

How to create an OST file?
1. Go to the Tools menu. (If using Outlook 2007)

Go to File>Info>Account Settings. (If using Outlook 2010)

2. Click Account Settings

3. You will find Microsoft Exchange under Email section. Double-click it.
4. Click More Settings.

5. Go to Advanced tab and click Offline Folder File Settings. Then, click OK to open the Offline Folder File Settings dialog box.

6. Type the desired file path in the File box and click OK.

If the default OST file (Outlook.OST) doesn’t exist you will get a message:

Click OK to create the default OST file (Outlook.OST)
If the default OST file Outlook.OST already exists then, you need to create the new OST file with different name.
7. Click OK
8. click Next,
9. Finally, Click Finish.

How to delete an Offline Folder (.OST) file?
1. Close Outlook client
2. Go to Start >Run.
3. Type  "%APPDATA%\Microsoft\Outlook\"
4. Click OK
5. From the Explorer window locate the .ost file to be deleted.
6. Select the OST file to be deleted then, press DELETE

You can also click the Delete icon from the Outlook toolbar to delete the selected OST file

Like other data files OST files are also prone to corruption. OST corruption will hamper the proper Outlook functioning. In such case you need to repair the corrupt OST file to resume normal Outlook functioning .But sometimes, the corruption level is so high the corruption is so severe that OST repair tools couldn’t help then, it’s better to delete the OST file and create a new one.