Delete OST
Open up Control Panel
Do View by Small/Large Icons in the right corner and select Mail
Click Data Files, Then click open file Location
youre gonna see these two files
.nst and .ost
just right-click rename and add .bak to both files. Do this while outlook is closed.
Then reboot outlook. IT will re-pull all emails from the server and should alleviate the problem.
Let me know if you need any assistance!