I’ve been running my own e-mail servers for decades. After all, back in the 80s I was helping run NASA Goddard Space Flight Center’s e-mail systems and let me tell you in those days it wasn’t easy! Today, thanks to easy e-mail servers such as CapeSoft Email Server, hMailServer, and Zimbra pretty much any tech savvy user can run an e-mail server. Heck, if you’re a step above a power user you can even run OpenExchange and fully support Outlook users without breaking a sweat. If, that is, your Internet Service Provider (ISP) will let you do it.
As a recent Slashdot reader found out, many ISPs won’t let you run your own mail server. Specifically they block port 25, the Simple Mail Transfer Protocol (SMTP) port, which is used for sending mail. If you can’t send mail, there’s not much point in having a mail server.