Weird, I’ve never had problems over the past 15 years or so and I’ve been using VPS servers exclusively. Maybe my providers were reputable enough.

I realize my evidence is only anecdotal, but that’s why I started “in my experience”. Also, common blacklists are checked by the services I mentioned.

In my experience, this is nothing more than an urban legend at this point. There are great standards, like DMARC, DKIM, SPF, proper reverse DNS and more, that are much more reliable and are actually used by major mail servers. Pick a free service that scans the publicly visible parts of your email server and one that accepts an email that you send to them and generates a report. Make sure all checks are green. After an initial day of two of getting it right, I’ve never had trouble with any provider accepting mail and the ongoing maintenance is very low.

Milage may vary with an unknown domain and large email volumes or suspicious contents, though.

Exactly this. This procedure is so common that you need to take care in situations where you don’t want the headers, as some tools set them per default.

Everyone keeps saying that but I just can’t see it. The only time my mails were rejected was because I didn’t know what I was doing at the beginning of my journey. Now, whenever I changed my stack or did some major updates the past 20 years or so, I just go to 2-3 sites that analyze my mail server from the outside and tell me if there is anything wrong. The free tier is always more than enough. Just make sure there is at least one service in the list where you send an email to a generated mailbox and have it analyzed. Just looking at the mail server is not enough to find all potential configuration issues.

I aim at a100% score. It’s time consuming the first time around but later it’s just a breeze.