Please elaborate more on the blocking, such as what IPs should be whitelisted.

I’ve been using SnappyMail and can’t complain.

“.home.arpa” for A records.

I run my own CA and DNS, and can create vanity TLDs like: a.git, a.webmail, b.sync, etc for internal services. These are CNAMEs pointing to A records.

Scaleway offer up to 75GB of their Object Storage for free and only start charging when you go over.

Check out FireQOS. I use it to prioritise traffic over my networks.

If you are using static ips/subnet per container, then it’s fairly straightforward to use with Docker.