Korthrun

Have you looked for providers that offer ETRN? Seems like that might fit your use case well.

I’ve hosted my own email for over a decade with very few issues. It’s low ram and CPU usage so a very cheap VM (or a pair in different locations if you wanna be leet) can be a viable way to avoid the ISP related issues people have trying to host it at home. If you really want it all ending up at home you can do ETRN as mentioned and while TCP/25 is often blocked at home, the submission port (TCP/587) rarely is.