Mail-in-a-Box - simple email server

It should be noted that email servers, no matter the setup, require you to follow strict standards to achieve proper delivery. It's very easy to get blacklisted, and it's next to impossible to get off of said blacklist once you're on it.

I used to host my own mail server with this, but it got to be too much to get my emails to actually send. I was always wondering if my email was actually delivered or if it was silently bounced or sent to spam. Email is the only thing I'm not willing to self host.

I'm absolutely in the "don't self-host email" camp. That said, I think it could be done reliably if you wanted to use someone else's SMTP server and let them worry about deliverability. As in, have your mx records on your domain route to your MTA and dovecot, but set your DKIM and SPF records to match a third party SMTP server. You could use mxroute as an SMTP server very cheaply. There are others like the email API type services. I still can't think of why I'd want to self host with all this drama but just an idea I've heard.
So is that why send mail won’t work for sending myself emails about a system? Once upon a time you could do that, but now no more is what I’m reading between the lines, sans a proper mail server??
- Yep, pretty much. It used to be doable, but these days it's very difficult. It's certainly not impossible, but one slipup and you could get on the deny list forever. It's just not worth it, since emails are usually pretty mission critical, imo.
Yea, if you are not willing to be meticulous about learning/understanding all the DNS stuff (SPF/DKIM/DMARC), and plan to host this at home, don't.

I ran this same system for a very long time on a VPS and had no problems with blacklists, but I'm also a career systems engineer that maintained enterprise systems and exchange servers.

Also note how I am speaking of MIAB in the past tense...

I think the better option is to try and avoid email as much as you can, just like SMS. Outdated tech and not secure. At that point, any ol' existing email service is good enough.
- I don't think the SPF / DKIM / DMARC stuff is overly complex nor the core of the problem.
  
  In my case it was recipients with bonkers microsoft exchange servers that just had weird ideas about who should be sending them emails.
  
  For example, one thing that tripped me up forever ago was grey listing. Apparently the receiving server just wouldn't acknowledge the sending server for an arbitrary period of time, say 12 hours or so. Spam senders would usually give up long before then, while a legit server would keep trying because it's legitimately trying to deliver an actual email.
  
  So my email-in-a-box type self hosted set up was fine really. Compliant you might say. But to send emails to this one in a thousand recipient I had to investigate what was going on and reconfigure things to ensure their server would interact with mine.
  
  Another thing that can happen is that spammers just put your email address in the "from" field and fire off a few million emails. Obviously the DKIM signatures and SPF won't match but it still just makes your future legitimate emails look spammy. Having the credibility of a larger organisation goes a long way in this type of instance.

Step 1: Cut a hole in the box (open a port)

I drank a glass of port.
Now what?
- Join your ship’s surgeon for an evening of Boccherini duets
- Shotgunning box wine?
Isn't that step two?

I feel like step one was "get a box," but I could be misremembering.
- skip to 1:45 for actual instructions, or watch the whole thing
  
  But step 2 is put your junk in the hole.

Ive used this in the past to host an email server. Eventually, my ISP actually stopped allowing people to use mail ports, so I had to discontinue. But it worked very well when I used it many years ago.

Its perfect for a small VPS. Been using it for years.

I do occasionally get places where my email simply will not send to them, even though it follows every email standard properly and isnt blacklisted. For those rare occasions, ill use a third party email address to send, which then forwards everything to my main email.
Call them and tell them to open it. It probably isnt legal for them to close the port if you ask them to open it.

MailCow is similar except uses docker. I expect that will mean easier maintenance as it is less tightly bound to the underlying OS.

I think Mailcow is a fair bit further along in features than this. I used this for a short bit but wasn't overly impressed, and you are right about how running a docker stack is less hassle for updating.

I've always been looking for an all-in-one mailserver with a few added features like mailing lists and something like AnonAddy (anonymous mail forwarding). Sadly there doesn't seem anything like that out there. So I have to configure postfix and dovecot myself. Or make ends meet with a bit more basic features.

Did you try docker-mailserver?
Check out stalwart mail! Not sure it has all the features you need, but it is really flexible through scripting and has got a nice admin web-interface!
- Thanks, and I happen to already be aware of it. It doesn't have any of that. And it's more complicated to hook it into other things, since the good old postfix is the default case and well-trodden path. I think I'll try Stalwart anyways. It's a bit of a risk, though. Since it's a small project with few developers and the future isn't 100% certain. And I have to learn all the glue in between the mailserver stuff, since there aren't any tutorials out there. But both the frontend, and the configuration and setup seem to make sense.

Lol no