Yes, installed by default. I find a lot of “how to” here: CentOS 6 - MAIL Server - Log Reports - AWstats : Server World
I used “how to” from here and it works, but I think this “must be” 
Don’t you think that AWStats offer more informations?
Again, YES!
It’s useful when you have only one Public IP on RED and you have at least 2 servers on ORANGE that use in the same time http or https (E-mail Server with Webmail and Web Hosting, …). It’s nice to do this from UI (for me, will be great!)