Delta Chat blogged about their release of chatmail services – email services optimized for powering end-to-end encrypted chat like DeltaChat.
With some knowledge of DNS, SSH and a spare VPS (get the cheapest you can find), you can setup and offer chatmail services yourself pretty quickly. A friend easily recently set it up on a Raspberry Pi for his housing project. Chatmail servers are designed to run with minimal hardware requirements and to be easy to tweak even from novice sysadmins or programmers. No permission is needed from our side to run a chatmail server. We might not even know you are doing it because Delta Chat has no tracking or counting.
Visit the deltachat/chatmail repo for instructions on install and setup.