Resources · Original Research

Numbers no one else publishes.

NeverSpam runs one of the largest seed-mailbox networks in the deliverability industry — 100,000+ real Gmail, Outlook, Yahoo, and iCloud inboxes, sending and receiving over two million probes per week. We publish what that data shows, with the methodological honesty the rest of the industry avoids. No vendor-pitch graphs, no cherry-picked vanity stats. Just the rates, the failure modes, and the surprises.

Seed mailboxes

100,247

Probes analyzed

12.4M

Mailbox providers

Research window

6 months

↳ Latest report

New · May 2026Original Research · Annual Report

State of Cold Email Deliverability 2026

Original research from 12.4M warmup probes across 100,247 real seed mailboxes — what works, what is broken, and what mailbox providers actually care about.

Published 2026-05-12·~4,800 words·28 min read

Read the report →Methodology

Top-line findings

01Median inbox placement on real campaign content dropped 11 points YoY (74% to 63%).
02Template-based warmup outperformed sender-only warmup by 28 percentage points across 14,392 cold campaigns.
03Yahoo inbox placement is now harder than Gmail for cold senders (39% vs 57% median).
041 in 4 senders with perfect DKIM/SPF/DMARC still hit spam due to content fingerprinting.
05Gmail content-fingerprint weight increased meaningfully after the March 2026 algorithm shift.

Data window

2025-11-01 → 2026-04-30

Confidence

95% CI throughout

In the lab · upcoming

What we are publishing next.

Coming next · Q3 2026Working title

State of Email Warmup 2026

Methodology benchmarks for warmup vendors. Which ramp curves, content strategies, and inbox-rotation schedules actually convert to real-campaign placement.

Subscribe at the foot of any report to get notified.

Coming next · Q1 2027Working title

The Spam Folder Census 2027

Recurring annual: what percentage of legitimate B2B sales email ends up in spam at the four major mailbox providers, segmented by domain age and authentication posture.

Subscribe at the foot of any report to get notified.

Editorial position

Why a warmup vendor is publishing primary data.

Every other deliverability stat you have read in 2026 was either three years old, traced back to one self-reported survey, or invented for a sales deck. The industry runs on borrowed anecdotes.

NeverSpam is in a position to actually measure this. We operate the seed mailboxes. We control the probes. We know what folder each test landed in, on what date, at what provider, after which warmup pattern. We are publishing the data because the deliverability conversation deserves better numbers — and because we trust our own product enough to show our work.

Every report cites its methodology, sample size, and confidence interval. Data requests for academic and journalistic use: research@neverspam.com.