Obviously there’s a ton in successful email hosting since it’s not just configuring few services. Proper DNS-records and privilege controls are mandatory, you need to occasionally clear up your domain/IP from spamlists (specially at the start) and single mistake can ruin your DNS reputation quite quickly which then takes time to build back.

But it’s still perfectly doable and, when you have proper knowledge on how the whole circus actually runs, not too difficult either. Only problem is that there’s no longer money on just email hosting since cloud hosting offers much more than just emails for the price a small gamer can’t just compete with. At least around here.