Mapi32.dll errors are caused by situations that lead to the deletion or corruption of the mapi32 DLL file. In some cases, mapi32.dll errors can indicate a registry problem, a virus or malware infection, or even a hardware failure.

Follow these steps in the order listed to tackle the simpler solutions first.

Recover mapi32.dll from Recycle Bin The simplest possible cause of a "missing" mapi32.dll file is that you accidentally deleted it.

If you suspect this, but you've already emptied the Recycle Bin, you may be able to recover the file using a free file recovery program. Just make sure the file was working properly before it was deleted (that is, it wasn't malicious or corrupted).