I just use stalwart - mail, it's just one docker container, has bleeding edge functions like jmap and there is no need of deeper knowledge. I refer my domain on the settings and got a list of all needed dns-records.
It takes 2-4 days to get SSL and dmarc answers from the big mail-players and if there is nothing wrong with your IP or your records then there is no mail going into spam of someone else.
What was the question? Find the typo? Well looks like the poll has a good result.