KNOWLEDGE BASE
Clear explanations of the protocols behind reliable email and DNS.
Guide
What is DMARC and why do Gmail and Yahoo require it?
DMARC tells receivers what to do with mail that fails SPF and DKIM, and sends you reports about who is sending as your domain.
GuideSPF explained: the 10-lookup limit and how to stay under it
SPF lists which servers may send mail for your domain. Too many includes and it silently breaks.
GuideDKIM: selectors, key length and rotation
DKIM signs your messages with a private key; the public key lives in DNS under a selector.
GuideEmail blacklists (DNSBLs) explained — and how to get delisted
What DNS blacklists are, which ones matter, and what to do when you are listed.
GuideMTA-STS and TLS-RPT: enforcing encrypted mail delivery
Make sure mail to your domain is delivered over verified TLS, and get reports when it is not.
GuideHow to read a Domain Health report
What the score means, how categories are weighted and what to fix first.