I was thinking of a mail server for not very technical people that is easy to install and update. The use case I'm thinking is let's say I have a domain like f

I was thinking of a mail server for not very technical people that is easy to install and update. The use case I'm thinking is let's say I have a domain like foo.bar. Each user gets a sub domain like user1.foo.bar. User 1 can send emails to anyone with an email address of .foo.bar but nobody else. User 1 can get emails from anyone at anything* at user 1 dot foo dot bar For example, facebook at user 1 dot foo dot bar The main benefit this project would have is zero customization. No setting is customizable and the whole thing is an appliance that keeps itself up to date. Thoughts?