Custom Message Board Website Needed

I need a website made. Users must be able to register. The site is essentially a bunch of message boards. Message boards are not threaded. They are just one long list of posts in chronological order. Users should be able to send messages to any message board the want. any replies on any message board including a user's name in brackets ([]) will also be sent directly to that user's inbox. It's quite simple really. Design should be just as simple.