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Email Deliverability & DNS Blog
Short posts — the stuff we wish someone had told us before a Friday outage.
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How to Check If Your Mail Server Uses Spamhaus Public Mirrors Before April 8, 2026
Spamhaus turns off public DNS mirror access on April 8, 2026 — queries via 8.8.8.8 or 1.1.1.1 return NXDOMAIN. Check and fix in 10 minutes.
→DMARC p=none vs quarantine vs reject — Which Should You Use and When?
Which policy to set today — none, quarantine, or reject — based on your reports.
→SPF Too Many DNS Lookups — How to Find and Fix the Problem
Count includes, spot the provider blowing the 10-lookup cap, flatten or consolidate.
→SendGrid DMARC Alignment — The Complete Setup Guide
SPF alone won't align Return-Path — three CNAMEs from Sender Authentication.
→Your DMARC Is Set to p=none. Here's Why That's Still a Problem.
Green tick, zero blocking — spoofing still lands in inboxes. What to do next.
→The SPF Lookup Limit: Why You Hit 10 and How to Stay Under It
Silent PermError when you stack one more SaaS on SPF — count and flatten.
→DMARC Alignment vs DMARC Policy — The Difference Most Guides Skip
p=reject doesn't help if alignment never lines up. Here's the split.
→Why Your Emails Pass SPF and DKIM But Still Fail DMARC
Two greens and a red — alignment is the missing piece.
→The SendGrid CNAME Setup Most People Miss
SPF include alone won't align Return-Path — you need the three CNAMEs.
→Subdomain Takeover: The Dangling CNAME Risk Nobody Checks
Deleted the app, left the DNS — someone else can claim your hostname.
→How to Read a DMARC Aggregate Report Without Losing Your Mind
Zip, XML, pain — or paste into the analyzer and get a table.
→Domain Expiry: The Infrastructure Failure That Always Comes at the Worst Time
NXDOMAIN Monday — auto-renew and WHOIS checks beat heroics.
→When Is It Safe to Set DMARC to p=reject?
You need clean aggregate reports for 2-4 weeks before p=reject is safe — here's exactly what to check.
→Why Your PTR Record Is Killing Your Email Delivery
No PTR record = many mail servers reject you before checking SPF. Here's how to add one.
→How to Set Up DMARC Alignment for Mailchimp
Mailchimp's domain verification is not the same as DMARC alignment — here's what's missing.
→SPF include: Explained — What It Does and When to Use It
Every include: costs one DNS lookup. Here's what include: actually does and how to use it without hitting the limit.
→The Email Authentication Checklist — SPF, DKIM, DMARC Before You Send
Five checks to run before sending from a new domain — and the order that matters.
→DMARC Subdomain Policy (sp=) — When You Need It
Your DMARC record covers your root domain — but what about mail.yourdomain.com? Here's when sp= matters.
→IP Warm-Up for New Sending IPs — The Right Way
Sending high volume from a new IP immediately is the fastest way to get blacklisted. Here's the right warm-up approach.
→How to Check DMARC, SPF, and DKIM from the Terminal
dig and nslookup commands to verify your email authentication records without opening a browser.
→Google Postmaster Tools — What It Shows and How to Use It
Postmaster Tools shows your domain and IP reputation at Google. Here's how to read it.
→Bulk Sender Requirements in 2024 — Google, Yahoo, and What's Coming
Both Google and Yahoo now require DMARC, SPF, DKIM, and unsubscribe compliance. Here's the full list.
→DKIM Key Rotation — How to Rotate Without Breaking Email
Rotating DKIM keys without downtime requires publishing the new key before switching. Here's the exact sequence.
→Choosing a Domain Registrar for Email — What to Look For
Not all registrars make DNS management easy. Here's what matters for email authentication setup.