Same story. Ran a set of about 20 postfix mail servers for my company. Prided myself on being proactive, setting everything up correctly. Using things like DANE even before they were mandatory but the trouble was always random blocking which was outlook.com 90% of the time and occasionally yahoo and Deutsch telekom. At least the latter provided contact details and were helpful getting things unblocked but Microsoft had horrific support. You are blocked, we won't or can't tell you why, nothing in the mail management system shows you any problems so we can't tell you what to fix, please see this 15 year old guide as to how to setup email properly and we will tweak the setting a bit to let your mail through until the next time we decide to block it.

So frustrating because they have no legal obligation to accept our emails but our product relies on them being delivered.

I gave up and moved everyone over to SES instead.

Had no problems at all self-hosting for two decades; then a provider went bust and I lost my static IP block, and with it its two decades of reputation.

I still self-host, but now I cheat for deliverability: route the problematic destinations (I'm looking at you, Outlook) through Amazon SES. At a few cents for five-figure numbers of emails, it's as close to free for personal/vanity email quantities as it gets to have someone whose full time job it is to make sure outgoing mail stays deliverable on your side while still keeping everything else under your control.

One thing to note is that Amazon are not very good at keeping amazonses.com up to date, so despite including it you can't set DMARC to hard-fail SPF or you will have mail bounce days.

I'm running 4 email servers, the oldest is from 2011 or so, to this day.

4 different countries, different AS.

I'm always puzzled by all the issues described by others. I had about 4 issues during these 15 years, all 4 were solved by reading the bounce message and doing what was asked in the message (contacting support of the destination).

A lot has changed, in fairness. Stalwart + LLMs can help with the full-time email administrator part. It's a lot easier than it was.

And on the deliverability side, using SES for sending avoids this entirely. Yes, ok, not fully self-hosted I suppose, but it's close enough (and for most people, the bill will be pennies).

I take a middle path. Self-host receiving mail, and use smtp2go.com for outgoing

Yes I figure if I’m going to pay someone to resolve a domain to an IP address I might as well pay the same person to operate my mailbox. Having clients that sync the mailbox offline is “local” enough for me.

This seems to depend so much on the IP address space one is in. I have never experienced deliverability issues after the first year–and that's since the 2010s iirc. The first year I had to ask several friends to send me emails first, or dig out my email from spam and reply to it. After that it worked flawlessly for Gmail, which was hit-or-miss before. A single ISP I had to write to manually–the person responding to my mail explained that they blocked emails from my hoster's IP range wholesale but made an exception for my IP explicitly.

Never had any issues since then, though I did have to adjust to new standards such as DKIM, DMARC, SPF etc. over the years.

I think the timeline is critical here and should be highlighted. Self hosting email server was something that worked out just fine in the past (used to host until 2014), however things have changed a lot with the scale of abuse. its not worth it unless you are doing it as a business. Sending a email from your home IP to big email providers with reliability is next to impossible. Even if we discount the spam management,

1. IP reputation is a big deal, its not just about not being on some blocklist, call it a cartel at this point, its about being on the allow list for other mail providers

2. Keeping it reputable is a continuous effort

That’s something I have hard time explaining to the business.

Yea we do all the best practices but still no one can guarantee 100% deliveries. Just not possible for e-mail.

Yes we can have 100% over a year but after that it still is a lottery, can’t say anything about future not having suddenly 40% not delivered

I have had my own e-mail server since 2017, and there is only one instance where I know I had a delivery problem, and in that case it was funny, because I wrote to two people who had the same e-mail server, and one got the e-mail the other did not. So probably a SPAM issue, but certainly nothing my e-mail server could have done better...

AFAIK, that case in 2019 was the only time an e-mail went missing.

you can check your delivery rate with services there are lots that are free to check and they also offer to "warm" your reputation. I have not done that yet (money!) and outside this:

- Outlook.com consumer mail addresses

you can still get >99% delivery rate if you have spf, dkim and all the new cool stuff.

So no, please DO NOT recommend against doing it because ONLY if mail stays a decentralized service providers will stay forced to not blacklist everything but other large providers.

Will second this, as someone that took the same path. Alternatives like Fastmail are so, so cheap when compared to the headache of building, maintaining, and troubleshooting a DIY stack. For something as fundamental as email you really want to choose the solution that gives you NO problems, rather than some solvable but troublesome problems at regular intervals.

Just too critical of a component in most people's lives to accept any level of unknowns in.