Deliverability insights
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DMARC Alignment Failures: Why You Still Fail DMARC With SPF and DKIM Passing
The most misunderstood part of DMARC. Why your record says "pass" but the From domain doesn't align — and how to fix both SPF and DKIM alignment.
MX Records Explained: What They Are and How to Check Yours
MX priority, multiple MX records, MX vs A records, and the three misconfigurations that make your domain silently undeliverable.
How to Set Up DKIM for Google Workspace (Step-by-Step With Screenshots)
Admin Console → Apps → Gmail → Authenticate email. The whole setup in ten screenshots, plus the two common "DKIM is not active yet" gotchas.
Instantly.ai Deliverability: How to Monitor and Improve Inbox Placement
Instantly's built-in warm-up + rotation is a good start, but it isn't enough alone. The extra checks to run on each sending account every week.
How Many Cold Emails Can You Send Per Day Without Getting Banned?
Provider-by-provider sending limits, why 50/day is the new safe ceiling, and how to scale beyond with inbox rotation.
Email Bounce Types Explained: Hard vs Soft and What to Do About Each
5xx vs 4xx, reject vs defer, what Gmail's "our system has detected" really means, and the bounce rates that wreck your reputation.
Mail.ru, Yandex and Rambler Deliverability: The Only Guide for CIS Markets
If your audience is Russian-speaking, Gmail tests tell you almost nothing. How the three big CIS providers filter mail differently from Western ISPs.
Inbox Rotation for Cold Outreach: How to Set Up and Why It Matters
Multiple sending domains, sub-domain separation, round-robin inboxes. The right rotation setup to send 1000s of cold emails a day without burning reputation.
Sender Reputation Explained: How Gmail, Outlook and Yahoo Score You
What a reputation score actually is, what ISPs measure, and the five things a sender can control to push their score upwards in ~30 days.
PTR Record and Reverse DNS: Why Missing rDNS Kills Your Deliverability
Forward-confirmed reverse DNS, why Gmail silently rejects mail from IPs without a PTR, and how to set up rDNS on Hetzner, OVH, AWS and DigitalOcean.
European Email Providers: Deliverability Guide for GMX, Orange, LaPoste, Free.fr, T-online, WP.pl
Your Gmail test tells you nothing about Germany, France or Poland. How each major European ISP filters mail — and why one test covers them all.
Apollo.io Email Deliverability: Avoid Spam When Scaling Outreach
Apollo's shared-IP sending pool is a blessing and a curse. The Apollo-specific tweaks that keep you inboxing when other users torch the reputation.
Yahoo Spam Filter: How It Differs From Gmail and What Senders Must Know
Yahoo is still 8% of US B2C recipients. Its complaint loop, its IP-level reputation weighting, and the three things Yahoo punishes that Gmail doesn't.
How to Automate Inbox Placement Tests With AI Agents (MCP + Claude)
Give Claude Desktop or Cursor the Inbox Check MCP server and let the agent run tests, diagnose placement, and propose DNS fixes on its own.
How to Set Up DKIM and SPF for Microsoft 365
Defender → Email & collaboration → Policies & rules → Email authentication settings. Every click, plus the CNAME gotchas that trip up admins.
BIMI: How to Show Your Logo in Gmail and Yahoo Inbox
A full BIMI rollout — SVG Tiny PS, VMC, DMARC p=quarantine prerequisite — plus whether the $1,500 VMC is actually worth it for your brand.
SPF Too Many Lookups: How to Fix the 10-Lookup Limit
Why SPF flattening is half a solution, how to audit your lookup count, and the cleanest fix — dedicated subdomains per vendor.
Mailchimp Deliverability: Why Your Campaigns Land in Spam
Shared IPs, free-tier senders, "via mailchimp.com" in your headers. The Mailchimp-specific reputation problems and how to work around them.
Tracking Pixels in Cold Email: Do They Help or Hurt Deliverability?
The data behind image-trackers. Why a 1×1 gif correlates with 12% lower Gmail inboxing — and when it's still worth the hit.
HubSpot Email Deliverability: How to Test Before You Send
HubSpot's own "Sent" metric isn't inbox placement. A quick pre-send loop that adds real placement data to your HubSpot workflow.
ProtonMail, iCloud, Zoho, Fastmail: How Privacy-First Providers Filter Your Email
They're smaller but their users are harder to convert. How privacy-first ISPs rank your mail and the three things that get you into their inboxes.
Woodpecker vs Lemlist vs Instantly: Deliverability Compared
We ran the same 100-email campaign through all three. Inbox rates, warm-up behaviour, and where each tool silently hurts deliverability.
Google Postmaster Tools: How to Read Your Domain Reputation
The only honest window into how Gmail sees you. What each metric means, what "Medium" reputation actually costs you, and how to move each needle.
Custom Tracking Domain: Why You Need One and How to Set It Up
Default shared tracking domains are often blacklisted. How to set up a CNAME-based custom tracking domain in Lemlist, Instantly and HubSpot.
The Most Common SPF/DKIM/DMARC Errors (Based on 1,000 Tests)
We analysed 1,000 real deliverability tests. The seven authentication errors that show up over and over — and the exact record fix for each.
SpamAssassin Score: What It Means and How to Lower It
What each SpamAssassin rule is testing, why HTML/text ratio trips honest senders, and how to go from 8.1 to 0.9 without rewriting your template.
Building an Email Deliverability Monitor With Our API (Developer Guide)
A 30-minute walk-through: Bearer auth, scheduled tests, SSE result streaming, and a Slack alert when a sender's inbox rate drops below 80%.
Shared and Dedicated Sending IPs: Who Controls What
A shared sending IP carries mail for multiple customers or streams under the provider's management.
Inbox Placement Rates by Industry: Who Gets to Inbox and Who Doesn't
SaaS, e-commerce, crypto, recruiting, financial services. Median inbox rates per industry and why the bottom two industries get filtered harder.