The fast way: in Safari or Chrome
- Save the .mpp attachment to your Mac (Downloads is fine).
- Open the MPP Viewer in Safari, Chrome, Edge or Firefox.
- Drag the file onto the page, or click to choose it.
You get the Gantt chart, the full task table with WBS numbers, dates, progress and predecessors, and the list of resources. Summary tasks fold and unfold. Viewing is free; there is nothing to install, so it works the same on an older Mac, a new Apple silicon Mac or an iPad.
Why not Parallels or Boot Camp?
Running Windows on a Mac means a Windows license, a virtual machine app, and still a Microsoft Project license on top, which is a lot of setup to read a plan. It's worth it if you build plans in Project every day. For opening the plans other people send you, it isn't.
Need it in Numbers or Excel?
The viewer exports the plan to Excel (.xlsx), which opens in Excel for Mac and in Numbers, and to CSV and a PDF Gantt chart. In Excel the outline is kept, so summary tasks group their subtasks and you can collapse them. Exports are $19 once for every project you open, with no subscription.
Opening .mpp files from Mail or Outlook
macOS doesn't know what an .mpp file is, so Quick Look can't preview it. Save the attachment first, then drop it into the viewer. If you get plans often, keep the viewer page bookmarked.
What about .mpx and .xml?
Older Project files (.mpx) and Project XML files (.xml) open the same way. If a colleague asks what to send you, either the .mpp itself or "Save As, XML" from Project works.