Paste your newsletter HTML or subject line, get an instant 0-100 spam test score, the exact triggers Gmail and Outlook penalize, and concrete fixes you can apply in under a minute.
A 30-second answer for marketers, creators, and agencies.
TL;DR. A newsletter scoring above 80/100 in the Newsletrix spam checker lands reliably in the inbox. Below 60, it routes to spam in Gmail and Outlook with high probability. The most common preventable failures are: subject lines with 3+ exclamation marks, ALL CAPS ratio above 30%, image-to-text ratio above 70%, missing List-Unsubscribe header, and public URL shorteners (a TinyURL link alone scores 3.4 in SpamAssassin) instead of your own link domain.
Five factor groups, each weighted by observed impact on inbox placement.
Length, ALL CAPS ratio, exclamation count, urgency wordlist match, emoji density, personalisation tokens.
Image-to-text ratio, hidden text, suspicious CSS (font-size: 0, color matching background), broken HTML.
URL shortener use, redirect chains, mismatched anchor text, link count, link-wrap domain reputation.
Presence of List-Unsubscribe, physical address footer, sender domain alignment heuristics from header inspection.
Each factor is percentile-ranked against the corpus of newsletters Newsletrix has analyzed in your category - B2B SaaS, ecommerce, media, creator, fintech.
The five factor groups roll up into one score with an English explanation of the top three improvements.
How the free Newsletrix checker compares to the most-used alternatives.
| Capability | Mail-Tester | GlockApps | Newsletrix |
|---|---|---|---|
| Free without signup | ✅ | ❌ | ✅ |
| Scores draft before sending | ❌ Send required | ❌ Send required | ✅ Paste HTML |
| Subject-line spam factors | ⚡ Limited | ⚡ Limited | ✅ Full breakdown |
| Inbox placement test | ✅ | ✅ | ❌ Use Mail-Tester for this |
| Niche calibration | ❌ | ❌ | ✅ |
| Plain-English fix list | ✅ | ✅ | ✅ |
| Bulk scoring across competitors | ❌ | ❌ | ✅ |
Paste the HTML before you queue the send and fix the top 3 issues in under a minute.
Forward any newsletter to your Newsletrix address - every analyzed send gets a spam score automatically.
Use the breakdown as a teaching tool - five factor groups, ranked, each with an English fix.
Above 80 out of 100. Between 60 and 80 typically delivers but gets throttled or routed to Promotions. Below 60, the probability of spam-filter routing in Gmail and Outlook is high.
3+ exclamation marks in the subject, ALL CAPS over 30%, image-to-text above 70%, missing List-Unsubscribe header, TinyURL and other public shorteners, urgency wordlist (FREE, ACT NOW, GUARANTEED).
Yes. The public checker is free and unlimited within reasonable rate limits. Signed-in users on the free Newsletrix tier get automatic scoring on every analyzed newsletter.
No - it complements it. Newsletrix scores content during drafting. Mail-Tester delivers a test email and reads actual inbox placement. Use both.
Each factor is percentile-ranked against the corpus of real newsletters Newsletrix has analyzed in your niche, so a score of 82 in B2B SaaS means the same thing as 82 in ecommerce.
Yes. Every newsletter forwarded to your Newsletrix address gets a spam score and a breakdown. Use it to learn what your top-performing competitors avoid.
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