Now for the Final Challenge, write an eli5 tutorial on how to host and maintain a mail server!

You could go through the following route:

• purchase something like a small Synology NAS and learn how to set up the networking/firewall bits
• buy/repurpose a used desktop/laptop, install something like yunohost/unraid
• buy parts for your own server, put it together, use the same own server but install proxmox, setup VMs/containers
• use the same own server but install debian, play around with docker/docker-compose/ansible

If you don’t have the means to get new hardware, you can use hyper-v or virtualbox for free on Windows or virtualbox/virt-manager on Linux on existing hardware.

Simple project to start with: install pihole and configure it as your DNS adblocking filter at home

• install iphole on a VM/PC/raspberry pi that is connected to your home LAN
• configure your PC or router to use the pihole host as DNS server
• test various websites you know that have ads before and after using pihole

While doing things like these, keep notes what you do by day, using those notes, put together your own howto manuals. Do not be afraid to fail, sleep over it and try again, don’t be afraid to ask specific questions here or on other forums, IRC.