Guides and answers on SPF, DKIM, DMARC and email deliverability, written from the RFCs.https://themaildoc.co/en-gbhttps://themaildoc.co/health-library/dmarc-guide/https://themaildoc.co/health-library/dmarc-guide/The only record that governs the address your recipient actually sees. What it does, what it does not, and how to reach enforcement without breaking your own mail.Thu, 13 Aug 2026 00:00:00 GMThttps://themaildoc.co/health-library/email-authentication-guide/https://themaildoc.co/health-library/email-authentication-guide/Three records, three different jobs, and only one of them stops somebody sending mail in your name. Here is what each proves and the order to fix them in.Thu, 13 Aug 2026 00:00:00 GMThttps://themaildoc.co/health-library/email-deliverability-guide/https://themaildoc.co/health-library/email-deliverability-guide/Deliverability problems have a small number of causes and a reliable order to work through them. Authentication first, because it is the only part you can prove.Thu, 13 Aug 2026 00:00:00 GMThttps://themaildoc.co/health-library/free-dmarc-checker/https://themaildoc.co/health-library/free-dmarc-checker/No account, no trial, no report held back behind an email address. Here is what it checks and what makes a DMARC check wrong.Thu, 13 Aug 2026 00:00:00 GMThttps://themaildoc.co/health-library/google-yahoo-microsoft-sender-requirements-2026/https://themaildoc.co/health-library/google-yahoo-microsoft-sender-requirements-2026/Three receivers, one shared list of requirements, and rejections rather than filtering when you miss them. Here is what each one asks for.Thu, 13 Aug 2026 00:00:00 GMThttps://themaildoc.co/health-library/how-to-fix-spf-too-many-dns-lookups/https://themaildoc.co/health-library/how-to-fix-spf-too-many-dns-lookups/Ten is the limit, the lookups inside your includes count against it, and past ten SPF fails for every message you send. Here is how to get back under.Thu, 13 Aug 2026 00:00:00 GMThttps://themaildoc.co/health-library/how-to-set-up-dmarc/https://themaildoc.co/health-library/how-to-set-up-dmarc/From no record to enforcement, in five steps. The first takes ten minutes; the rest are mostly waiting and reading.Thu, 13 Aug 2026 00:00:00 GMThttps://themaildoc.co/health-library/mxtoolbox-alternative/https://themaildoc.co/health-library/mxtoolbox-alternative/What this does differently, what it does not do at all, and an honest note on when the other one is the right tool.Thu, 13 Aug 2026 00:00:00 GMThttps://themaildoc.co/health-library/p-none-vs-quarantine-vs-reject/https://themaildoc.co/health-library/p-none-vs-quarantine-vs-reject/Three policies, one of which protects nothing. What each does to your mail and how to move between them without breaking anything.Thu, 13 Aug 2026 00:00:00 GMThttps://themaildoc.co/health-library/what-is-dkim/https://themaildoc.co/health-library/what-is-dkim/A cryptographic signature on every message you send, and the only identifier that survives being forwarded.Thu, 13 Aug 2026 00:00:00 GMThttps://themaildoc.co/health-library/what-is-dmarc/https://themaildoc.co/health-library/what-is-dmarc/The only email record that looks at the address your recipient actually sees, and the only one that stops somebody sending in your name.Thu, 13 Aug 2026 00:00:00 GMThttps://themaildoc.co/health-library/what-is-spf/https://themaildoc.co/health-library/what-is-spf/A published list of the servers allowed to send for your domain, and the ten-lookup limit that quietly breaks a lot of them.Thu, 13 Aug 2026 00:00:00 GMThttps://themaildoc.co/health-library/why-are-my-emails-going-to-spam/https://themaildoc.co/health-library/why-are-my-emails-going-to-spam/Six causes, in the order worth checking. The first two you can prove in about a minute; the rest take longer and matter less often.Thu, 13 Aug 2026 00:00:00 GMT