I use both IONOS for domains and webhosting and a VPS from Host Unlimited, they also offer webhosting, but I haven’t tried it yet. I’m happy with both. Host unlimited apparently has a tier with unlimited mailboxes.

Volumes are horrible, how would I easily edit a config file of the programm running inside, if the container deosnt even start.

Bind mounts + ZFS datasets are the way to go.