Email authentication guides and tools
Practical, vendor-neutral explanations of SPF, DKIM and DMARC, and free tools that measure them from public DNS.
Guides
Why SPF permerror happens at the 11th lookup and five ways to get back under the limit without dropping senders.
DMARCA staged rollout for DMARC enforcement that does not lose legitimate mail.
DKIMThe DKIM selectors used by Google Workspace, Microsoft 365, SendGrid, Mailchimp, HubSpot, Zendesk, Postmark, Amazon SES and others.
AGENTSHow to hand a measured fix plan to Claude Code, Cursor or ChatGPT, what to make the agent show you before it touches DNS, and how to verify.
Free tools
Expand every include, count DNS lookups against the limit of 10, and see what to change.
Find published DKIM keys across 70+ common selectors and verify key strength.
Validate policy, percentage, alignment and external report authorisation.
The full include tree with the lookup cost of each branch.
Comparisons
Pricing per domain, trial, free tier, report analysis and monitoring, side by side.
vsPricing per domain, trial, free tier, report analysis and monitoring, side by side.
vsPricing per domain, trial, free tier, report analysis and monitoring, side by side.
Recently graded
Public checks from the last few days. Every report is re-measured from DNS when opened.
Monitoring, not just checking
Every guide ends the same way: records drift and nobody notices. MailAuthWatch re-checks your domains daily and alerts you on any change.