outlook.pst is not valid
 

If you are getting this message again and again, it's mean your PST is corrupted and need to recover PST file. Use PST repair tool allow to recover corrupted and deleted data from Outlook PST file and restore into new healthy PST file that can be open with any MS Outlook version.
Read more- http://www.securasecurity.org/tag/outlookrecoverytool/

Your PST file is corrupted and need to repair by using RecoveryFix for Outlook recovery software which is embedded with advanced algorithms that ensure the recovery is quick and precise. It searches all lost, inaccessible, unusable emails, recovers and restores them into new PST file. This tool provides two modes of recovery such as Standard mode and Advance mode.


Read more-http://www.recoverytool.org/outlook-pst-recovery.html