Email Authentication
4 postsPlain-English guides to SPF, DKIM, DMARC and the other DNS records that prove your email is really from you and keep it out of spam.
RSS feed
Paul O'Brien DMARC Explained: What Happens When Email Auth Fails DMARC passes only when SPF or DKIM passes and aligns with your From domain. Here is what a DMARC fail means and how to fix it. Email Authentication8 min read 
Paul O'Brien SPF Explained: What It Proves and Why It Fails SPF lists which servers may send email for your domain, but it checks the delivery path, not the sender people see. This guide covers record syntax, ~all vs -all, the 10-lookup limit and why legitimate mail fails. Email Authentication9 min read 
Paul O'Brien SPF, DKIM & DMARC: How Email Authentication Works Email was built on trust, so the From line can be faked. This guide explains how SPF, DKIM and DMARC work together, adds MX, MTA-STS and BIMI, and points to the detailed guide for each. Email Authentication6 min read 
Paul O'Brien DKIM Explained: What It Proves and Why It Fails DKIM signs your email so receivers can check it wasn't altered, but it proves integrity, not identity. This guide covers signatures, selectors, key length, provider setup and why genuine mail fails. Email Authentication7 min read 