I'm really afraid e-mail is going away though. Most people today would rather message via Facebook and this article goes into how unreliable it is to run your own e-mail server due to Microsoft/Google's over aggressive spam filtering: http://penguindreams.org/blog/...
MS/GOOG didn't start that; SPAM scoring did. I started having delivery problems from my consumer grade connection a decade ago. Now it's virtually impossible to deliver email from an IP address in the dynamic database.
Every ISP I've had runs an SMTP relay (I'm currently on Time Warner). I tell postfix to relay most things through it. I'd prefer not to, but it's going over their wires, so they can already read it if they want to.
[clewis@hacker ~]$ grep 'transport_maps'
transport_maps = hash:/etc/postfix/transport
[clewis@hacker ~]$ tail -4
Whoops. Likes like I should update that config. RoadRunner was bought out years ago. IIRC, I got smtp-server.roadrunner.com from their email client setup instructions.