Well, sure, not dangerous like underwater welding, or electrical powerline installation or something, but it's something that requires constant attention to do right.
Even people who do their homework and start out vigilant, can eventually develop entropy and then 3 years later you get a message from your host telling you your machine is being used for spam - like this guy who is also coincidentally on the front page:
https://news.ycombinator.com/item?id=12384880
Sure, it's not dangerous, but it's awfully time consuming if/when things go wrong.
Perhaps, but that can be said of most things. Model rocketry, glass blowing, hell even woodworking. That doesn't mean people shouldn't roll up their sleeves and get into it because 'some megaultracorp has perfected the process', for some incredibly generous definition of 'perfected'.
Running your own server does in fact take some time and a little bit of elbow-grease, but scare-articles like this does nothing to further an open internet. As the tech-elite (for the most part), we should be encouraging folks to host their own data, learning how 'those damn computers' work, and do our best to raise the next generation of engineers, sysadmins, devopsen, docker deployers, or even just computer dabblers 'right' so they at least have some concept of How The Internet Works(tm) beyond "oh, send this dict to an API...". If hosting your own email server is too scary for you at this time, suck it up, do it anyway, and figure out what needs to happen to make it better for the NEXT guy. Write down what breaks and when. Publish that data. Let us learn from your fail, as you learn from ours. Holler at your nearest Google or Comcast or Centurylink engineer, suit, or peon to un-fsck their infra. It's not glamorous work, but it is necessary.
As fun as it was, I now find it less hassle to just outsource that to a third-party that specialises in it.
Really, the likelyhood that something terrible happens to your own email setup isn't all that great. Not much greater than that something terrible happens because someone breaks into your web browser, say.
What it costs in a year is less than the time/effort it would cost me to maintain a fully patched and up to email date server.
If you're the type who understands why not to do it, but does it anyway "for fun", that's probably OK because you understand the risks and what types of bad things can happen (and probably have some idea of how to prevent and/or fix them).
If you don't and "just install OwnCloud" or whatever the flavor of the week is for "own your whole social stack by installing linux on that dusty tower sitting in your garage and STICK IT TO THE MAN!", you're likely setting yourself up to get your identity stolen at the very least, with having the FBI come and seize all of your electronic equipment not out of the picture, e.g. in the case of some hacking crew using your poorly-secured box as a proxy / jump host / C&C / worse. No thank you very much.
I know most of this stuff because I've been there, and the people like me who have done it for years and see the horrors are honestly trying to help those who might be tempted. I set up exim with SpamAssassin and clamav on Debian before I could drive with my own bind server hosting all the zones out of the basement, Server 2k3 running AD, Zimbra and slapd + freeradius on opensuse. I did it to learn, and after getting it all set up (which took weeks back then) and getting inbox deliver to gmail (again, in a time when doing so had a much lower bar), I thought I was some kind of Internet wizard. I did learn a ton before my first tech job doing this, and I also learned why it was a bad idea. I got a letter from my ISP a few weeks after getting this all online (of course I had remote access set up via pfsense with SSH on a non-standard port with root login disabled) informing me that there was a botnet C&C running at our home IP. Figuring this was just a mistake, as I was active on IRC at the time, I dug into the traffic and basically found that what the ISP said was true. I was able to set up a mitm on pfsense to get a log of the IRC activity in order to figure out exactly what was going on. Most of my set-up had been taken over without me even realizing it.
Quite a few years later, I worked in web hosting for a few years. The amount of terrible things which happened to unmanaged colos and dedicated servers was astounding. There were quite a few legal disputes which involved data on systems we physically controlled. There were companies which went out of business due to data loss. There were others which were blackmailed by hackers. Others simply went under. There wascredit card theft, databases dumped, unsalted passwords, you name it, and plenty more we probably didn't know about. The Internet was a very hostile place for a server years ago, keeping hackers busy looting and pillaging. I'm sure it's much worse now, with more profit to be made, tons more stuff to be pwnt, and tons more people launching poorly-configured stuff.
Leave the MTAs to the pros. I promise that somewhere out there, someone is getting paid a good amount to spend quite a bit of time keeping that mail server online and in good shape. They are very likely better at this than you, have way more clout with their domains than you (no one cares if your domain / NS / netblock / AS gets blacklisted, but if gmail / yahoo / aol / Comcast stops working, postmasters@ all over will jump to fix it), and are getting paid to do it, likely as a full-time job, likely for many systems. You may be able to set it up once, and make it work a few times, until it annoys someone who cuts it off, at which point you have very little recourse and very little chance of ever making it work as well again.
The point isn't that you can't do it, the point is that it's not worth the risk when there are so many other great options out there.
Granted it's still too difficult for Joe User but initiatives similar to Sandstorm may make it a reality one day.
So your saying google (and a few others) broke a fundamental part of the internet?
Yes, yes they did.
I run my own mailserver for personal email as well as for rsync.net and 0x.co. It's trivially easy to do from a technical standpoint and simple to lock down to prevent abuse.
The problem is that yes, in fact, google/gmail will drop email, by default, into gmail users' spam folder from a privately run email server.
Specifically, I mean that with squeaky clean IP addresses from your own squeaky clean private allocation, with a mail server properly configured with DKIM signing and a DMARC record, etc., etc., and 10/10 non-spamminess scores from mail-tester.com, you will be treated as spam by default by gmail.
It's total horseshit. It's "evil".
If the most simple, least common denominator, least technically challenging aspect of being a peer on the network is thwarted by google, how will they behave towards things that are actually interesting ? How will we run our own asterisk exchanges and create our own micro-cloud-hosts and host our own websites from a routable ipv6 address that we have in our home ?
That alone is the reason to not use gmail, if any of you think it hasn't happened to you, trust me it will.