SPF: These are the servers I will send from. If it says it's from me, but comes from somewhere else, it's likely fake DKIM: This is my signature, if it's not on the email, it probably didn't come from my server. DMARC: If you get mail that doesn't match the above, here's what I want you to do with it. --- From: https://www.reddit.com/r/sysadmin/comments/16gvtdj/comment/k0aidyz