1. It's a massive exaggeration that it's dangerous to run your own email server. Now, he doesn't explain why he thinks that it is, but I guess there would be two major categories, both based on the assumption of vulnerabilities: (1) your server could be abused against others (yes, but so could your laptop or smartphone) or (2) your own emails could be at risk of being leaked (yes, but the solution to that obviously is not to directly give them to someone else instead).
2. None of that is actually solved by simply trusting someone else to run your email servers for you if you also can't judge whether they are doing it properly and, in particular, in your interest.
3. If you think that trusting someone else to run your email servers for you is an acceptable solution, that is functionally equivalent to trusting someone else to provide you with a software package to run on your email servers. Everything that someone else could do on an email server that they run for you, they could just as well package into, say, an install CD image, which you then could use to run your own functionally equivalent, hopefully well-configured and well-updated, mail server.
So, I would think, this is at best an argument against putting together your own mail server from distro packages, and configuring everything yourself, maybe.
Other than that, there is no fundamental reason why you would need to know email RFCs any more for running an email server than you need to know them for running an email client. In either case, knowing them can help you with figuring out some problems. But also, in either case, if the software is good, the programmers should have taken care of reading the RFCs for you, so you don't need to, for the most part.
2. None of that is actually solved by simply trusting someone else to run your email servers for you if you also can't judge whether they are doing it properly and, in particular, in your interest.
3. If you think that trusting someone else to run your email servers for you is an acceptable solution, that is functionally equivalent to trusting someone else to provide you with a software package to run on your email servers. Everything that someone else could do on an email server that they run for you, they could just as well package into, say, an install CD image, which you then could use to run your own functionally equivalent, hopefully well-configured and well-updated, mail server.
So, I would think, this is at best an argument against putting together your own mail server from distro packages, and configuring everything yourself, maybe.
Other than that, there is no fundamental reason why you would need to know email RFCs any more for running an email server than you need to know them for running an email client. In either case, knowing them can help you with figuring out some problems. But also, in either case, if the software is good, the programmers should have taken care of reading the RFCs for you, so you don't need to, for the most part.