Personal folders are often the main cause of many problems related to Outlook. Microsoft has published the Inbox Repair tool, Scanpst.exe, that can be used to scan .pst and .ost files for errors in the file structure. If this is not intact, it will reset the file structure and rebuild the headers. This tool will only work on the files that reside on your computer’s hard drive, not the files on the Microsoft Exchange Server. This will also help to resolve the error message: “Cannot open your default e-mail folder.