Cannot open your default email folders. The file xxxx.ost is not an offline folder file.

Problem:

When starting Microsoft Outlook, you get the following error message: Cannot open your default email folders. The file xxxx.ost is not an offline folder file.   Resolution: There are two reasons that will cause this error, as follows: ·         The OST file is damaged or corrupted, and cannot be recognized by Microsoft Outlook, so Outlook will report this error. ·         The OST file is associated with a mailbox on the Exchange server. If for any reasons, Microsoft Outlook cannot access the associated Exchange mailbox or start synchronizing the mailbox with the offline folders in the OST file, it will report this error.   Solution: 1.    Find the OST file that causes the error. 2.    Rescue the offline data in the OST file.use Advanced Exchange Recovery to scan the OST file, recover the data in it, and save them into an Outlook PST file. 3.    Backup the OST file. 4.    Rename or delete the original OST file that causes the problem 5.    Make sure the email account settings in Outlook are correct, and Outlook can connect to your Exchange server correctly. 6.    Start Outlook and send/receive your emails on the Exchange mailbox, this will make Outlook to create a new OST file automatically and synchronize its data with the Exchange mailbox.