Beacause these types of services go to great effort to keep their repuation high on email services. You use these services so your 1000's emails get delivered instead of being rated as spam or being blacklisted.
Is there something special why you’d need to pay for a product such as mailgun, and not just something like the ISPmail guide suggests?
Both for small bootstrapped projects, and for larger companies it should be cheaper to just run it yourself.
That is most definitely not the norm. Entire ISPs get blacklisted on a regular basis, working around that is difficult.
There are a lot of hurdles to hosting an email service, and some of them are geographic, and out of your immediate control.
If things are difficult... Why wouldn't you pay to make the hassles go away all together?
It’s just, I can’t believe that it’s just luck that I never had these issues. Is it luck? Is it because people try configuring email without such tutorials (which actually would be quite complicated)? Is it because people with no devops experience try it?
On the other hand, if a devops engineer can set it up in a day, it’ll cost you ~270€ (taking a usual European salary for such a person), which would you get 27000 emails with this service. So it might actually be worth it.
It’s certainly not impossible but takes more work as you scale up. I think that’s part of the attraction of these services. Pay for it to be their problem (in theory anyway) :)