It remains a constant frustration to me that Postfix, Exim, Cyrus, Dovecot and the like still feel as if they belong very much in the "here be dragons" territories of the Unix world. Configuring these systems is an exercise in constant frustration and bafflement. They're such a pain to use that since becoming the sysadmin in charge of our work email servers, I gave up running personal ones as well and just pay FastMa…
The result is that now when you are configuring SMTP you have to also configure DNS. That means more things that can go wrong, and more things to check as you are setting things up.
It also means you may need to pay a fee for a domain name. This is because we all submit to the notion of an ICANN root and commercial registrars selling (renting) names that cost nothing to create. Thus email is not solely under your control. You generally have to play the ICANN DNS game, only because your email recipients are playing. Nothing stops anyone from running their own root though. And this is what is done with private DNS inside organizations.
And then, as if that DNS complication was not already enough to take control of email away from you, you have various schemes trying to prevent spam that discriminate for or against mail you send based on IP address and domain name.
Can you operate email without DNS? Technically yes. There was a time before DNS, and email worked just fine. Practically speaking, today you need DNS, whether it's under ICANN's root or your own.
All this hassle steers you to just accept third party email hosting. Profiting from this arrangement has become a career for many a man. And with "the cloud" many are hoping to cash in yet again, as organizations who once ran controlled own email feel pressured to let a cloud computing vendor control it for them.
The fact that all this third party control makes warrantless search and surveillance so easy is but one side effect. Centralising hundreds and thousands of accounts in third parties make the spammer's job easier, too. If you think about it, there are many unwanted side effects of centralizing email. When every sender and recipient are connected directly to each other via a network, why would you want to prevent them from sending messages to each other directly?
With the constant connectivity and bandwidth we have today in many places, the centralisation and outsourcing of email is baffling to me... it is nonsensical... until you remember how much of a PITA it is setting up email.:)
It's no wonder we let third parties handle it. Is this PITA by design? Who cares? Let's just fix it. More of these projects should exist. Or made public (I imagine many of these are personal setups now being released for public use). I have my own that uses qmail.