That's actually kind of the problem. It's the same thing with phone systems. Any IT person worth a shit can follow a decent tutorial and end up with a system that works. Until it doesn't.

What happens when it doesn't is the issue. For a lot of businesses this will be an immediate critical problem. This is not a great time to be learning by experimentation.

If these services are not critical then go nuts, but if your business depends on these services you really want to have someone whose full time job it is to run them. If your business is not large enough to support having a person's primary role be administering these systems you should really have a third party vendor do it for you.

The article is right, you don't have to use one of the big names, but most of the time it's not a good idea to run your own if you consider email to be a critical service.