The following fixtures can be applied to fix Outlook as well as ost related errors.
Technique 1: End All Background Processes
Open the Task Manager and right click on it (you can also select ctrl + alt + del key)
If you want to see all background processes then click on”processes” tab
You can look for Outlook, Communicator, Ucmapi Or, Lync
If any of the above items found then press the “End Task”
Technique 2: Disable Cache Mode for Exchange
Close Outlook properly(also make sure about background processes)
Go through Control Panel > Mail option > Email Accounts > Email tab
Choose email address and hit on Change and uncheck the Cached Exchange Mode and finally click on finish
If you are unable to open OST file then there might issue with integrity of OST file. You can run scanost tool to fix corruption issues of OST file (Scanpst tool in Outlook 2007 and above versions). But one problem using this solution is that it will produce a healthy PST file but remove corrupted parts of OST file also. hence one can loss some parts of their crucial data.
Technique 3. Choose any best third party solution
Third party solutions prove to be the best approach in such circumstances, as it will repair corrupted parts of OST file without harming original ingredients of OST file as well as convert OST to different file format. These types of software have very easy to use GUI interface so that any novice user will not face any difficulty. Installation of software is very easy as well as it opens your ost file just in seconds. In my knowledge, you check detailed here; http://www.microsoftosttopst.com/
. Perhaps it is avialble in its free trial run.