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.