mailbox.org and skiff are „too expensive“ with 3€/month.
Ah... I do use mailbox.org and I've self-hosted with docker-mailserver before.
I agree, selfhosting mail is a really big pain, and at least where I live most ISPs don't open the ports necessary for mailservers, so I had to spin up my own server & it was more expensive than just using a mail provider. Could potentially be the cheapest option if I could host it from home & just use a RasPi or something
I'm happy with mailbox.org; the Standard Tier price is 2.50 Euro/mo if paid in full if that helps. Probably not the cheapest option especially since it's not unlimited, but they do allow domain matches at Standard tier or above, and there are other goodies like calendar/video conferencing/cloud storage & stuff.