I'd like to point to another smtp server, which I am using and is much easier to set up than postfix in my opinion, especially for small servers like mine: https://www.opensmtpd.org/ I'm running a personal mailserver (opensmptd, dovecot, dkim, spf, dmarc, spamassassin) for some years now and although I initially had problems with deliverability to google there aren't any (apparent) issues so far. Also I don't underst…
Details of my current setup are here:
https://github.com/cullum/dank-selfhosted
Though this will be out of date soon since I'm moving everything over to Illumos...I have a fondness for dying operating systems I guess!