Type a subject line, then hit test. Everything runs in your browser, nothing is sent anywhere.
Please type a subject line first.
Score
0/100
Mobile inbox preview
Your Business
Most phones cut subject lines after about 35 characters. What survives the cut is what gets opened.
Detailed checks
Quick wins
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Get a Free ConsultationFrequently asked questions
Is this a real spam filter test?
No. This is a transparent heuristic checklist, not a real spam filter. Real deliverability depends on your sender reputation, authentication, and list quality, which no page can measure.
How is the score calculated?
Length is worth 40 points (41 to 50 characters is ideal), avoiding spam trigger words is worth 35, engagement hooks like questions and numbers add up to 15, and a personalization token adds 10. Penalties apply for all-caps words and extra exclamation marks.
Why does the mobile preview matter?
Most phones cut subject lines after about 35 characters. If your key words sit past the cut, many readers never see them, so front-load the important part.
Preview
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