Well, it depends what you call spam, how well known your server is (are your email addresses spread far and wide on the web or only known to a couple of people) but a lot of spam is automated and algorithmic, so most servers will be showered with speculative mail addressed to likely mailboxes - which your server still has to process, if only to bounce the message; if you have antispam measures, your server can just drop the connection when it detects a spammy sender (e.g. from an address on a black or greylist). I’m not currently running any mail servers, but a few years back when I did, I used to get about 80% spam incoming.

The list is immense, and I didn’t want to clutter my post with all the details. So just listing off things that spring to mind (because I don’t know what OP doesn’t know):

• Choosing an MTA - sendmail, postfix, exim, etc. and why you might choose one over the others
• Firewall settings
• Software/package management on your chosen distro
• Learning about DNS:
  • Host it - yourself via BIND
  • Or via a DNS service provider
  • DNS record types
    • Domains
    • Subdomains
    • A records/CNAMEs
    • MX records
    • Mail authority records - SPF’s
    • Mail encryption records - DKIM
• Spam filtering, anti-virus
• Learning how to configure your MTA, which requires learning:
  • the configuration file language your MTA uses
  • what all the options mean and what they do
  • what the bare minimum options are to get up and running
  • how to make sure your configuration is secure and won’t be exploitable by bad actors
  • how mail really gets delivered
  • how to setup secure smtp
  • how to set up SPFs
  • troubleshooting why GMAIL or Microsoft won’t accept your mail
  • troubleshooting why GMAIL or Microsoft have stopped accepting your mail
  • dealing with blacklists/greylists when someone sends too many messages, or something that “looks too spammy”
• Mail hosting pitfalls
  • Being an open relay
  • Rate limiting
  • Reputation management
  • Vulnerabilities that let a hacker take over your server
  • Resource management - disk, memory, processes, queues, etc.
  • Downtime when you need to do updates
  • Downtime if you change your DNS configuration

I’ve definitely missed some stuff, and each of those things requires knowing other stuff too, so you can see that it’s really a pretty deep subject. This is precisely why not many people self-host email themselves these days - the big guys have made it harder and harder to do so, in the name of eradicating spam, which they themselves are the biggest vectors for.

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.

Listening to “Down in a Hole” by Alice in Chains whilst reading this… seems to fit. Thanks for this. Food for thought.

Yep. Currently working through Autistic Burnout, and one of my symptoms is Dissociation. Whenever I’m slightly stressed or concentrate hard on something, it kicks in. My head feels a bit “spinny”, but I’m not dizzy; I feel a bit “high”, but without the pleasant buzz of weed; when I move around, I kind of feel like a floating balloon on a string being pulled round by a toddler. My interoception (internal sense) is terrible at the moment, so I don’t get body maintenance signals like need to pee or drink, until I’m almost desperate, and I feel emotionally numb - I mostly seem to only “feel” strong negative emotions, positive ones if felt at all are pretty distant. I also get visual snow - like TV static in my vision - and a “laggy” feeling, which is often independent of, but somehow connected with the dissociation, which feels like living in a 3D game with too low a frame rate - my perception of my movement becomes stuttered, almost like there is a strobe light on, and it feels like I’m moving through treacle. It’s a bundle of fun.

Edit: I’d also intended to say, but I got distracted by my cat asking for food, that I hope you feel better soon. I’m sorry you are having to live through this. I find for me, it takes a few days to a week to wear off after I’ve been stressed - it seems to peak a day or so later, and then peter out over a number of days, as long as I avoid stress. I hope you can avoid your trigger.

In 2011, I worked in West Bromwich, greater Birmingham, UK, on Birmingham Road, where it joined High Street. The news had been reporting on riots starting in Tottenham, London, and it was said that they were spreading. One lunch time during this time, I went out to get lunch from a great Indian sweet shop called Dhillons that did an amazing Samosa Chaat, which was about 5 minutes walk down the road from our office. As I got closer, I could see a crowd and police further down the road, not far from the sweet shop, and coming towards me. Then I saw smoke, and turned around, and went back to the office, without my samosa chaat. Loads of busies with full blues and two’s on (police cars with sirens and lights on) started whizzing past, towards the trouble, and this continued all afternoon. When I left, the air was cloyed with smoke, and the street towards the sweet shop was cordoned off. The next day we learnt that the sweet shop got smashed up, and their van was torched, one of many that got hit. Nearly got caught up in a riot!

We don’t have a TV at all.