Please do not do this.
Putting organic material into a landfill where it will decompose anaerobically (without oxygen) creates methane. This methane then leaks from the landfill, accelerating climate change.
There are SO many constructive things you can do with organic material. You can take a dead or dying tree, or one that is otherwise a poor fit for a particular location, and use it to make wood chips for mulching soil; biochar to sequester carbon and enrich compost when added to compost; building materials; firewood and more. All of these things sequester carbon and/or reduce climate emissions by reducing the use of fossil fuels.
Growing a healthy tree just to make some methane with it in a landfill is profane. Please don't send any organic material to a landfill, especially not healthy trees. Leave healthy trees alone unless they're causing trouble (such as by damaging a roof) and instead prioritize the use of dead/dying ones, or those that aren't appropriate for their spot (e.g. shading solar panels) or climate (e.g. trees that require irrigation).
DNS, web, mail, WireGuard, etc. I wrote the webserver in about 700 lines of Go and the other software is by other people. Currently I'm rewriting everything in Rust and will write an authoritative DNS server in Rust. Eventually I want all my services to run on my own software (except for WireGuard, which is best in-kernel).
My first professional mailserver was around 1996, with 400 users, up to over 3000 users by 2001. It was awesome then but now mail is the last thing I'd recommend anyone self-host. The ecosystem has been deteriorating for decades at this point.