Deliverability insights
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Why Our Seed Network Sits Outside Every Warmup Pool
A placement test that uses pool-resident mailboxes grades itself. Here is how we keep the seed network independent and why it matters.
Russian and CIS Inbox Testing Free: Mail.ru, Yandex, Rambler, List.ru
CIS inboxes are a separate filter stack that most Western tools ignore. We seed all of them and test placement for free.
Complete Microsoft Coverage: Outlook.com, Hotmail, Live, Office 365
Microsoft runs at least four overlapping mail systems with different filter stacks. We seed all of them separately.
Gmail Personal vs Google Workspace: The Hidden Placement Divide
The same message can land Primary on consumer Gmail and Junk on a Workspace tenant. Why the two Gmails filter differently.
Per-Seed Placement Detail: Not Just a Percentage — See Every Mailbox
Competitors report 'Gmail: 72%'. We report every seed mailbox, its folder, its auth verdict, and the raw headers.
Authentication Audit + Placement Test in One Free Report
SPF, DKIM, DMARC, BIMI, MTA-STS, PTR — all validated. Placement across 30+ providers. Both halves of the deliverability picture in one report.
Inbox Check for Agencies: Multi-Client Monitoring, Free Tier That Scales
Agencies managing outbound for multiple clients can monitor them all on the free tier. Tagging, per-client dashboards, API, webhooks — no per-seat fees.
OAuth for Zapier, Make, n8n: Placement Tests in Your Automation Stack
Standard OAuth 2.0 lets Zapier, Make, n8n and any automation tool call Inbox Check natively. Triggers, actions, real authentication. Free.
No Signup, No Credit Card: A Placement Test in 30 Seconds
We don't ask for your email to run a placement test. Paste the draft, pick providers, go. The anti-friction policy and why we chose it.
iCloud, GMX, Web.de, Zoho, ProtonMail: We Cover the Long Tail
Most tools cover Gmail and Outlook well and leave everyone else as a footnote. We test iCloud, ProtonMail, GMX, Web.de, Zoho and more.
We Screenshot Your Email Across Providers: Catch Layout Bugs Before Customers Do
Every Inbox Check run captures rendered screenshots across providers. See exactly how your email looks in Gmail, Outlook, Yahoo, Mail.ru before the customer sees a broken layout.
Gmail vs Outlook Rendering Differences: Our Screenshots Show You Both
Gmail and Outlook render HTML email very differently. Side-by-side screenshots expose the most common breakage points.
Dark Mode Email Rendering: Screenshot Every Provider, Free
Dark mode is where a third of email users live and where half of templates look broken. Our screenshots capture both light and dark variants per provider.
Mobile vs Desktop Email Layout: Our Screenshots Cover Both
60-70% of email is opened on mobile. 100% of design review happens on desktop. The gap is where campaigns break. We render both viewports per provider.
Email Screenshot API: Automate Visual Regression Testing of Every Campaign
Pipe email screenshots into your CI. Any template edit gets diffed against the last known good. Broken layouts caught before the campaign runs.
Why We Don't Do Warmup (And Never Will)
A manifesto. Warmup pools were a 2020 answer to a 2018 problem, and in 2026 they are a fingerprint filters can see. We refuse to add one — here is why.
What Gmail Actually Thinks About Warmup Networks
From public Gmail sender guidelines, ML research on coordinated behaviour, and placement-test data: how Gmail models warmup pools today and what that means for your placement.
We Spent $3,600 on Folderly. Here's What We Learned
A six-month case study of a paid warmup engagement. Raw placement numbers, dashboard vs independent tests, and the non-obvious lessons from reading the delta.
Real Warmup for Cold Email: The No-Bullshit Guide
What actually moves placement for a new domain: auth, verification, ramp discipline, content, monitoring. A 28-day playbook with no pool and no subscription.
How Google's ML Fingerprints Warmup Pools
Six signals every major provider can use to detect warmup pools: graph closure, template uniformity, reply latency, diurnal patterns, engagement co-occurrence, domain age.
Synthetic Engagement Signals Google Stopped Counting in 2026
What Gmail used to count that it now mostly doesn't — opens, synthetic replies, pool mark-as-important, tracking-pixel fires. And what it's counting instead.
Your Warmup Dashboard Says 95%. A Real Placement Test Says 40%
Why warmup tools report stellar inbox numbers that independent placement tests cannot reproduce. The measurement loop and how to audit your own tool in 30 minutes.
The 48-Hour Warmup Kill Test: Is Your Tool Doing Anything?
A 48-hour experiment any team can run. Pause warmup, measure real placement, compare to baseline. The cheapest audit before paying for another month.
Lemwarm vs Mailivery vs Warmbox: A Technical Teardown
Three popular warmup tools, what each actually does to your domain, and where their claims and reality diverge — based on traffic captures and 8 weeks of measurement.
9 Questions to Ask Before Buying a Warmup Subscription
A buyer-side checklist to separate warmup vendors whose pool is actually doing something from those whose dashboard just grades itself.
Ramping a New Domain to Real Prospects Without Any Warmup Tool
A 28-day ramp schedule to real cold prospects — no pool, no dashboard theatre. Volume curve, segmentation, checkpoints and what to monitor each week.
List Verification Before Warmup: The Priority Nobody Argues Against
Bounce rate has a bigger impact on placement than any warmup pool ever will. A checklist and verification stack that beats 6 weeks of warmup.
A/B Testing Cold Email Content Beats Warmup Volume Every Time
Subject line, first line, CTA, length — each variable alone moves placement more than a month of warmup pool traffic. What to test and how to measure it.
Bounce and Complaint Monitoring IS the Real Warmup Stack
Thresholds, tooling, alert policies and weekly checkpoints. What warmup vendors bundle and bill for — but you can build free in an afternoon.
Authentication-First: 72 Hours of Auth Work Beats 6 Weeks of Warmup
SPF, DKIM, DMARC, BIMI, ARC. What each does, how to configure them right, and why fixing them is a far larger placement lever than any warmup subscription.
Why Experienced Cold Email Operators Turned Off Warmup in 2026
A pattern survey of 40+ agency and in-house operators who dropped warmup subscriptions in the last 12 months. Their reasoning, what they replaced it with, and the outcomes.
Warmup Broke When Gmail and Yahoo Enforced Their 2024 Sender Rules
Gmail and Yahoo bulk-sender requirements in 2024, DMARC enforcement, and one-click unsubscribe shifted the ground. Warmup pools faced a layer they were not designed to defeat.
Warmup Dependency: When Reputation Collapses the Day You Stop Paying
Reputation propped up by pool traffic is fragile — it collapses the moment you pause. How to detect dependency and taper off safely.
The Small-Sender Warmup Myth: If You Send Under 500/day You Don't Need It
Warmup pools were pitched at high-volume senders but became a reflex purchase for 200/day founders. Why small senders never needed warmup and what to do instead.
How We Monitor Deliverability Without a Warmup Tool
Our daily and weekly monitoring stack. Free tools, scripted checks, alert thresholds and the weekly ritual that replaces a warmup subscription.
Yandex Mail Spam Filter: How It Works and How to Avoid It
Yandex's spam filter is ML-heavy and domain-reputation-first. What postoffice.yandex.ru shows, what it hides, and the five things to fix first.
Mail.ru Email Deliverability: The Complete Guide for Senders
50M+ active Russian inboxes. Postmaster.mail.ru setup, FBL loop, DKIM strictness, SPF alignment — everything to know before you send to Mail.ru.
Yahoo Sender Hub vs Google Postmaster: Which Gives Better Insights?
Yahoo finally has a postmaster portal. How its signals, sampling and layout compare to Google's — and which one to check first.
Yahoo and AOL Mail Sender Requirements 2026: How to Pass Compliance
Yahoo aligned with Gmail on DMARC, one-click unsubscribe and <0.3% complaint rate. What the 2026 update changed and how to audit your compliance.
How to Test If Your Email Reaches Outlook Inbox (Free Tool)
Outlook, Hotmail, Live and Office 365 all use different SmartScreen signals. A single free test that covers every Microsoft-hosted mailbox type.