

I’d suggest you start with a simple static web server if you’re looking for a good beginner project. Use something like Nginx, and just set it up on your local network at first, then work out how to harden it, and open it up to the real internet. There’s a lot less to learn for this usage case, and it’s less likely to get you into trouble.
I say that, because, after reading through the thread, it seems you are hoping to find an (educational) use for an old computer. I did Linux and Unix admin professionally for 15 years, for some famous brands. I would NOT recommend setting up a mail server as a first project - it’s complex in ways you will never expect, and will require learning skills and knowledge that are very specific and you literally can’t “start small and build up” because a lot of the things you don’t know yet will get you into big trouble. Essentially, it’s not too hard to set up the server software, and your hardware is certainly capable of running this task, but making it safe and secure IS hard these days - especially with all the encryption and anti-spam setups you have to learn how to do.






I guess I’m the heretic here - I’m currently using Cinnamon DE, after recently switching from MATE, which I’ve used almost exclusively for about 13 years. I always preferred Gnome (even v1) to KDE, but used both in the early 2000’s, but eventually settled on Gnome2 by about 2005, because it was what Ubuntu used, and that was the distro I was using back then. Later, when all the main Linux distros switched to Gnome3, about 2013, it wrecked my workflow - it simply wasn’t possible to do the things I needed to do - though I tried for a couple of months. Mainly things like lack of usable support for multiple monitors, full-screen-first app behaviour, rearranged key-bindings, etc. just made it impossible to work efficiently. I tried most of the commonly supported DEs - LXDE, XFCE, LXQT, plain X-Window(!) and even an early version of Cinnamon, but eventually settled on MATE when it became supported by Debian. I felt at home with it, and stuck with it for the longest of any of them - mainly because it fits my workflow, even through its evolution through different work roles and personal projects. I wasn’t really looking for a new DE, but last year, I refurbished a load of old laptops to give away on Freecycle/Freegle, initially putting Debian + MATE on the early ones. I saw a discussion about Linux Mint, and how it had matured into a really beginner-friendly system, and decided to try it out. I’m by no means scared of doing the technical work to get things running (I was doing tarball installs back in the mid 1990s) but I do appreciate convenience, and Mint was amazingly smooth.
I’d installed Ubuntu for my kids and friends over the years, and still hated the way Gnome3 works, even though it has evolved and some of my original gripes were now alleviated, so as Mint is based on Ubuntu, I was not expecting much. I was totally shocked - it was basically easier than Windoze 10 (which I was adminning for my day job) - printers and scanners, something that have long been annoying to support - worked instantly, and the Cinnamon DE was a revelation - smooth and friendly, and works well with how I like to use a DE. It runs well on old hardware - though 4GB seems to be the hard, workable minimum, and people seem to really like it.