please recommend some good source material mainly on spf but dmarc, dkim will be nice too. The information that I have found on the web so far treats the subject too generally, or are instructions on how to configure the above with a specific service provider. I would really like to understand the topic, so I am asking for help. Thank you in advance
Here's an article that I wrote on the subject: https://explained-from-first-principles.com/email/#domain-authentication