You could install a basic setup with a "apt install x x x" one-liner in ubuntu, and it would not take more than a few minutes to configure everything with sensible defaults.
The key here probably is, most people don't want to spend time learning enough about Postfix, Dovecot. Etc. To do that.
The key here probably is, most people don't want to spend time learning enough about Postfix, Dovecot. Etc. To do that.