Setting up a private server

I’d like to receive mails at my TLD, which is a premium feature for basically all mail providers I’ve seen. Having access to a (virtual) private server opens up the option to run a private mail server though. This seems like a daunting task because of the many moving parts and security concerns. Luckily there are (external) NixOS modules for that - providing an abstraction layer on top of many packages and their configurations with sensible defaults: