Microsoft Outlook, which is a popular email client, stores all its program data either in “.pst” or “.ost” files. Outlook data related to email folders, contacts, calendars - everything is saved in these files. One advantage of this is that you could easily transfer all your Outlook data to a different computer by simply copying these PST or OST files. But there is also a negative aspect to it. If something happens to these files, your entire Outlook data could become obsolete. And that’s if you still retain any of it – there’s a chance you won’t be able to access any of the data, including the email messages. However, Microsoft Outlook lets you repair these damaged or corrupted PST or OST files using its built-in repair tool. Below are some Outlook repair instructions to troubleshoot problems associated with corrupted PST or OST files. Repairing the .ost file Close the Outlook application if it is running. Click on the Start button and select the option “Run”. Type “ dr...