That’s a little confused. From what I remember, it’s the server that matters, not the domain when being blocked. If you self-host this is a problem, but not if you use your own domain on a commercial service.
The “MX records and such” are all a function of domain management. You’ll have to do this whether or not you self-host.
In truth, the 70% was just one, low end product which could have been due to any number of factors. The other price hikes quoted were much more in line with the tarrifs.