Deliverability insights
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Microsoft 365 Email Deliverability: Why Outlook Treats You as Spam
M365 mailboxes are tenant-filtered on top of SmartScreen. The four M365-specific reasons your mail lands in Junk — and the fix for each.
Outlook / Hotmail Spam Filter: Why Your Emails Go to Junk and How to Fix It
SmartScreen runs on content signals Gmail ignores. The Outlook-specific triggers — and a 20-minute fix list that pulls most senders back to Inbox.
How to Test Email Deliverability to Gmail Without Paying for GlockApps
A free Gmail placement test that covers Inbox, Promotions, Updates, Social and Spam — across consumer and Workspace mailboxes.
Gmail Spam Filter in 2026: What Changed and How to Pass It
Gmail's 2026 updates tightened engagement weighting and DMARC enforcement. What shifted, how to detect if you are impacted, and what to change.
Gmail Inbox vs Promotions vs Spam: How to Test Where You Land (Free)
Three very different outcomes, same "delivered" status in your ESP. A free test that shows you the real Gmail tab — Primary, Promotions, Social or Spam.
Why Are My Emails Going to Spam? 12 Reasons and How to Fix Each One
From SPF misconfig to shouty subject lines — the twelve most common reasons your mail lands in Spam, with a concrete fix for each.
Best Free Email Deliverability Tools in 2026: Honest Comparison
Your ESP says "delivered" — but delivered where? A straight-shooting comparison of the 5 free tools that actually tell you whether your email reaches the Inbox, Spam, or Promotions.
Inbox Placement vs Delivery Rate: The Metric You're Ignoring
Your ESP's 99% delivery rate means nothing if 40% of it lands in Spam. Here's why inbox placement is the only number that matters.
Cold Email Deliverability: The Pre-Launch Checklist (2026)
The 17-point pre-flight checklist for cold outreach — DNS, warm-up, list hygiene, copy, sending cadence. Run before every campaign.
Gmail Spam Filter 2026: How It Works and How to Stay in Inbox
Gmail's filter uses ML on engagement, authentication, content and domain reputation. A practical breakdown of each signal and how to win at it.
What Is an Inbox Placement Test and Why You Need One Before Every Campaign
A smoke test for your email. What an inbox placement test actually does, how seed mailboxes work, and what you should do with the results.
Email Deliverability in 2026: The Complete Guide for Marketers
The only guide you need. Authentication, reputation, content, engagement — every deliverability lever explained in one place.
Emails Going to Spam in Outlook: 9 Fixes That Actually Work
Outlook's SmartScreen is stricter than Gmail. Nine concrete fixes for the most common reasons your mail ends up in Junk.
How to Warm Up a New Email Domain for Cold Outreach
A 4-week ramp plan for fresh domains: volume curves, engagement tactics, which warm-up services help, and which break you.
SPF Record: What It Is, How to Set It Up, and Common Mistakes
Everything about SPF in plain English. Syntax, includes, the 10-lookup limit, and the misconfigurations that silently kill deliverability.
DKIM Explained: How to Sign Your Emails and Why It Matters
What DKIM actually does, why Gmail demands it, how selectors work, and the two-line DNS record that gets you signing today.
Open Rate Is a Lie: Why Inbox Placement Is the Only Metric That Matters
Apple MPP, Outlook's blocked pixels, AI summaries. Why open rate has been broken since 2021 — and what to measure instead.
Why Your Cold Emails Land in Spam (and the 15-Minute Fix)
The three fixes that take you from 20% to 80% inbox: authentication, domain age signals, and removing the spam-trigger content patterns SDRs all copy.
We Tested 500 Domains: Here's Where Cold Emails Actually Land in 2026
Real data from 500 inbox-placement tests. Median inbox rate, the single biggest predictor of Spam placement, and provider-by-provider breakdown.
How to Check If Your IP Is Blacklisted (and How to Get Delisted)
Which blacklists matter, which to ignore, how to check all of them in one go, and the delisting process for Spamhaus, SORBS and Barracuda.
DMARC for Beginners: Set Up in 15 Minutes, Protect Your Domain Forever
No jargon. A 15-minute DMARC rollout from p=none to p=reject, the aggregate reports you should actually read, and the mistakes that lock out legitimate mail.
What Happens to Your Email After You Hit Send (Step by Step)
MX lookup, TLS handshake, RCPT TO, content scanning, filter routing. A guided tour of the journey from Send button to Inbox folder.
How to Check Email Deliverability Before Sending a Lemlist Campaign
Lemlist hands you the tools but not the verdict. A 5-minute pre-send routine that tells you whether your sequence will land in Inbox or Spam.
Email Warm-Up Tools Compared: Do They Actually Work in 2026?
Mailwarm, Warmup Inbox, Lemwarm, InboxReach, Warmy. What they actually do to your reputation — and which ones Gmail has started to catch.
Gmail vs Outlook vs Yahoo vs Mail.ru: Who Sends More to Spam? (20+ Providers Compared)
We ran identical messages through 20+ providers. The Spam rate ranking will change how you think about "deliverability".
Gmail Promotions Tab: Why You Land There and How to Get to Primary
The Promotions classifier isn't about being "promotional" — it's about a specific set of signals. Here are the eleven that matter.
Gmail and Yahoo 2024 Sender Requirements: What Changed and What to Do Now
DMARC mandatory, one-click unsubscribe, <0.3% spam complaint rate. A compliance walk-through for bulk senders still not aligned.
SPF, DKIM, DMARC: The Complete Authentication Checklist
One-page checklist covering every SPF/DKIM/DMARC record and alignment check you need to pass before sending a single campaign.
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.