Email deliverability, explained
Guides to SPF, DKIM and DMARC — what each record does, the bounces they cause, and the exact fix to paste in. Every page ends where the diagnosis starts: a free scan of your domain.
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Foundations
- UpdatedWhat is SPF? A plain-English guide →
SPF lets a receiving mail server check the sending server is authorized by the envelope domain. The record syntax, the 10-lookup limit, and what SPF misses.
- UpdatedWhat is DKIM? Signatures, selectors, and keys →
DKIM signs each email so receivers can verify it really came from your domain and was not altered. How selectors, key records, and rotation work.
- UpdatedWhat is DMARC? Policy, alignment, and reports →
DMARC tells receivers what to do with mail that fails SPF and DKIM alignment. How alignment really works, what each policy does, and the safe path to reject.
- UpdatedEmail deliverability: why your mail lands in spam →
What receiving mail servers actually weigh — authentication, reputation, blacklists, PTR, content — what a domain owner controls, and the myths to skip.
- UpdatedWhy monitor DMARC reports? What the data tells you →
DMARC aggregate reports list every server sending as your domain. Why the raw XML is unreadable, what monitoring extracts, and what enforcement-ready means.
- UpdatedWho requires DMARC now? Google, Yahoo, Outlook and beyond →
Google and Yahoo require DMARC for bulk senders since February 2024, Outlook since May 2025. Who requires what, at what volume, and where adoption stands.
- UpdatedDMARC monitoring after p=reject — why you're not done →
Reaching p=reject is the milestone, not the finish line. Why DMARC reports still matter at enforcement: new senders, silent drift, and mail that vanishes.
- UpdatedDNS propagation: what's actually happening, and how long it takes →
Why a DNS change shows up in one place and not another, why '24–48 hours' is a myth, what TTL really does, and how to verify a change has gone global.
How-to guides
- UpdatedHow to add a TXT record to your DNS →
Add a TXT record at Cloudflare, Namecheap, GoDaddy, Porkbun, Route 53 or Google Cloud DNS — with how to find which provider hosts your DNS.
- UpdatedConnect your domain to DNS Doctor monitoring →
The full walkthrough: create an account, add a domain, prove ownership, publish the rua record, backfill old reports, and read your first diagnosis.
- UpdatedDMARCbis (RFC 9989): what changed and what to do →
DMARCbis (RFC 9989) is the standards-track update to DMARC. What changed from RFC 7489 — np, psd and t tags, pct deprecated — and what your domain needs to do.
- UpdatedDNS MCP server — DMARC, SPF and DKIM tools for AI agents →
A DNS MCP server for AI agents: scan and fix DMARC, SPF, DKIM, MX, blacklists and expiry from Claude or any MCP client — hosted endpoint or local npm package.
- UpdatedDNS skill for AI agents — DMARC, SPF and DKIM done safely →
A DNS skill for Claude and other AI agents: the DMARC, SPF and DKIM workflow — scan, diagnose, fix with validated records — for Claude Code and OpenClaw.
- UpdatedPay per call: DNS Doctor's x402 burst lane for AI agents →
DNS Doctor's API now answers HTTP 402: past the free rate limit an agent can pay $0.01 in USDC on Base per call over the x402 protocol.
Provider setup
- UpdatedGoogle Workspace: set up SPF, DKIM and DMARC →
The exact SPF, DKIM and DMARC DNS records to authenticate email sent through Google Workspace (Gmail), plus where to paste them and how to verify.
- UpdatedHubSpot: set up SPF, DKIM and DMARC →
How to connect a HubSpot email sending domain with the account-specific DKIM CNAMEs, why they earn DMARC alignment, and how to verify it.
- UpdatedMailchimp: set up SPF, DKIM and DMARC →
How to authenticate a domain for Mailchimp campaigns with DKIM, why the CNAME matters for DMARC alignment, and how SPF and DMARC fit in.
- UpdatedMicrosoft 365: set up SPF, DKIM and DMARC →
The exact SPF, DKIM and DMARC DNS records to authenticate email sent through Microsoft 365 (Exchange Online), plus where to paste them and how to verify.
- UpdatedSendGrid: set up SPF, DKIM and DMARC →
How to set up domain authentication in Twilio SendGrid with its CNAME records, why Automated Security handles SPF and DKIM, and how to verify.
- UpdatedZoho Mail: set up SPF, DKIM and DMARC →
The exact SPF, DKIM and DMARC DNS records to authenticate email sent through Zoho Mail, which SPF include to use, and how to verify it.