Running your own mailserver is like your own mini-Vietnam war. Looks straight-forward, but you will soon be bogged down and stuck.
Trust me, use a 3rd party service.
Does not need to be mail chimp though. I am using these guys:
Crappy site, but good server. Just a well set up SMTP server, so with a few config lines from your app you can send mails through this instead of your own server.