It was our regular client trying to open his emails through Outlook. The problem he was having is although he could see Microsoft Outlook sending and receiving emails but was not able to open the email messages. We diagnosed the system and found out that the Outlook PST file was corrupted. We repaired the PST file and managed to fix the problem. PST stands for Personal Storage Table and is commonly used by Microsoft Exchange Client, Windows Messenger and Microsoft Outlook. This stores messages, calendar events and other items within Microsoft Software.