MBox Viewer

Description: MBox Viewer (or mboxview) is Windows GUI based program to view mbox files such as
Thunderbird Archives, Google mail archives or simple Eml files.
Interface: Windows GUI
License: Freeware
Tools: Local mail database viewer, portable
Homepage
Platforms: win32
Commentary: Useful for locally archiving and searching Google Mail exports (while minimizing cloud usage). 
Usage Example: Arrange files in a folder structure, run mboxview.exe

Screenshot: