MAPI.DLL is considered a type of Dynamic Link Library (DLL) file. Dynamic Link Library files, like MAPI.DLL, are essentially a "guide book" that stores information and instructions for executable (EXE) files - like SCANOST.EXE - to follow. These files were created so that multiple programs (eg. Office) could share the same MAPI.DLL file, saving valuable memory allocation, therefore making your computer run more efficiently.
Unfortunately, what makes DLL files so convenient and efficient, also makes them extremely vulnerable to problems. If something happens to a shared DLL file, either it goes missing or gets corrupted in some way, it can generate a "runtime" error message. Runtime is pretty self-explanatory; it means that these errors are triggered when MAPI.DLL is attempted to be loaded either when Office is starting up, or in some cases already running. Some of the most common MAPI.DLL errors include:
- Access Violation at address - MAPI.DLL.
- MAPI.DLL could not be found.
- Cannot find C:\Windows\System32\MAPI.DLL.
- Cannot register MAPI.DLL.
- Cannot start Office. A required component is missing: MAPI.DLL. Please install Office again.
- Failed to load MAPI.DLL.
- The application has failed to start because MAPI.DLL was not found.
- The file MAPI.DLL is missing or corrupt.
- This application failed to start because MAPI.DLL was not found. Re-installing the application may fix this problem.
Your MAPI.DLL file could be missing due to accidental deletion, uninstalled as a shared file of another program (shared with Office), or deleted by a malware infection. Furthermore, MAPI.DLL file corruption could be caused from a power outage when loading Office, system crash while loading MAPI.DLL, bad sectors on your storage media (usually your primary hard drive), or quite commonly, a malware infection. Thus, it's critical to make sure your anti-virus is kept up-to-date and scanning regularly.