How to open a mpp file Format
The MPP file type is primarily associated with ‘Microsoft Project’ by Microsoft Corporation. With Project you can set up projects, keep project teams aligned, and track and analyze projects.
Their are viewers available for Word, Excel and PowerPoint,But Microsoft does not provide an viewer for Microsoft Project (.mpp) files. It means if you don’t have the Project program installed on your system, you can’t read any of those project plans.
But you can see you project plan online with a free registration Here
Then you can see your Microsoft project plan like this.