If the background color in the target document is going to be similar to the one in 3ds Max, then this is the best I could come up with:
0. Our end goal is to get a result similar to the Corona VFB.
1. Enable direct visibility enviro override and set it to black.
2. Add a CMasking_Mask render element, include all objects in it, scroll down and disable "allow propagation".
3. Render and inspect the Beauty element. It should look like this.
4. Inspect the Mask element. It should look like this (all objects are solid white).
5. Save in any format, without alpha - I used PNG (settings attached).
6. Load both files into Photoshop. Apply the Mask to the Beauty. Save as PNG.
7. Load into PowerPoint.