openshift-ansible-kvm VS AnsiMail

If you need a full cluster to test, spin up some local vms and get ocp going. Here's a playbook for upi on kvm. Although if you really are testing things for prod, might want to talk the boss into a sandbox environment. Nothing is going to match your prod more closely than running it on the same infra type as your prod cluster. https://github.com/kazuhisya/openshift-ansible-kvm

I like their pricing structure for bulk accounts. What I'd absolutely love to see is more email services that are Protonmail compatible, utilizing WKD or whatever it they need. Here's something to look at anyway https://github.com/Excision-Mail/Excision-Mail

It's not trivial, but it's doable.

Excision Mail which runs on OpenBSD hits the majority of what you need technically. https://github.com/Excision-Mail/Excision-Mail

The bigger problem is finding a hosting provider that hasn't had their entire space blacklisted.

For that, you're likely going to have to pick a "responsible" provider, have a couple of rounds of back and forth with them to prove you're neither an idiot nor a spammer, and ask them to manually open the port for you. And they're going to demand something that will tie to identity.