I don't know any solutions for setting up a mail server easily. But my general opinion is that software is poorly written if it requires an arcane setup all kinds of moving parts.

Usability studies shouldn't just be focused on the UI but equally on the setup an maintenance of server software. You would need to find a balance though since you won't want to remove features just because of ease of setup.

Sorry for ranting a bit and take the discussion a bit off topic.

Software is complex but it would be nice if us developers put energy into making complex setups feel less complex. It might even benefit security and less malconfigured services.