On a slightly related note, Michael W. Lucas[1] is working on an upcoming book entitled "Run Your Own Mail Server", that will be published shortly (there's a Kickstarter campaign as well[2]).
I attended his tutorial and talk at BSDCan[3] this year and both were excellent. I highly recommend buying the book when it comes out (or supporting the Kickstarter), it will go through all the gory details of setting up and running a mail server, and best practices, including a ton of material on SPF/DKIM/DMARC.
(P.S. I have no affiliation with the author or the book in any way.)
I attended his tutorial and talk at BSDCan[3] this year and both were excellent. I highly recommend buying the book when it comes out (or supporting the Kickstarter), it will go through all the gory details of setting up and running a mail server, and best practices, including a ton of material on SPF/DKIM/DMARC.
(P.S. I have no affiliation with the author or the book in any way.)
[1] - https://mwl.io/
[2] - https://www.kickstarter.com/projects/mwlucas/run-your-own-ma...
[3] - https://www.bsdcan.org/2024/