Yes, instead of of discussing different levels of users, or different levels of computer systems, I tried to point on the route problem, not getting astray on tangents out of tangents, to steer the discussion onto a more constructive path.
The route problem is what I wrote. That we have applications that actually rely on mail, and that these do need an MTA to communicate with the user.
If this is a packaging problem, it should be addressed, and it would have been good if this had been taken care of before removing the MTA.