I have administered both Exim and Exchange and would very much like not to do so again. Especially since in the time since then the number of requirements for effective delivery and antispam has only gone up.

So have I and I agree with regard to exchange which I kicked to the curb as soon as possible. Exim? A breeze. Spam? Not a problem at this moment ]1] nor has it been for the last 10 years or so, filters are effective and low- to no-maintenance. The real fight now lies in getting your mail accepted by the likes of Microsoft and Google but that isn't as hard as it is made out to be. Annoying? Yes, it is a hurdle which needs to be taken. Once configured correctly it doesn't need any maintenance other than keeping DNS configuration up to date but that needs to be done anyway. Every now and then they come up with a new anti-competitive^Wspam scheme for which something needs to be configured somewhere but that's about it. I spend maybe 2-3 hours per year in maintenance of the mail system, time well-spent in my opinion.

[1] ...but LLMs have the potential to change that for the worse