Problem MAPI is the underlying messaging interface between third party programs such as NEO and Outlook message stores. This is a shared resource. A few, mostly older, 3rd party programs make changes to MAPI that can cause it to get corrupted, or make it unusable by other programs.
The symptoms of a corrupted message store are typically severe - you can't open any program that uses email.
This article provides steps you can take to solve the problem.
Resolution Do these steps first
Close NEO and Outlook.
Locate a utility program on your computer called FIXMAPI.EXE. The easiest way to find it is to search for it with Windows Find. When found, double-click it to run it. It will probably run quickly and may not produce any visible results.
Restart your computer.
Start NEO to see if your problem is resolved.
Do these steps only if the above steps do not fix your problem
Rename each occurrence of MAPI32.DLL on your system to MAPI32.OLD. The easiest way to find it is to search for it with Windows Find.
Reinstall Microsoft Outlook using the repair and replace missing or corrupt files option. This will install the correct MAPI32.DLL.