Email Tester
Most emails are won or lost before they are opened. The subject line, the preview snippet, and a handful of spam signals decide whether you land in the inbox or the promotions tab. Paste your draft below and get an honest 0-100 score with the specific fixes that move it — no sending required.
A strong campaign email has a subject of roughly 30-50 characters, 40-130 characters of preview text, no spam-trigger phrases (‘free’, ‘act now’, ‘guaranteed’), no ALL-CAPS or repeated !!, at least one clear call-to-action, and a sensible link-to-text ratio. This tester scans your subject, preview and body against all of those, scores the result 0-100, and lists the fixes in priority order. The ranges are widely used rules of thumb, not guarantees — always confirm with your own A/B tests.
Email Tester inputs and result
How to use this calculator
- Paste your subject lineStart with the subject — it carries the most weight. The tool scores length, ALL-CAPS, excess punctuation and spam triggers instantly.
- Add preview text and bodyPaste the preview snippet and body to score preview length, personalization, link-to-text ratio and CTA presence in context.
- Read the 0-100 scoreThe verdict tells you whether the email is inbox-ready, needs a few fixes, or is risky. The score reflects weighted penalties for each problem.
- Work the prioritized fixesAddress high-impact issues first (empty subject, heavy link ratio, ALL-CAPS), then medium and low. Each fix lists the exact change to make.
- Export your checkCopy a share link, download the CSV, or print a PDF for the campaign review, then A/B test the judgment calls.
RGM Expert Says
We score every campaign before it ships, and the same three problems account for most of the damage: a subject that truncates on mobile, a missing preview line, and a body that is mostly links. None of them feel like mistakes when you are writing fast, and all of them quietly cost opens and clicks. A two-minute lint pass catches them while they are still cheap to fix — which is the entire point of testing copy before the send instead of reading the post-mortem after.
Spam-trigger words are real but widely misunderstood. A single ‘free’ will not bin you; modern filters weigh sender reputation, engagement history and authentication far more than any keyword. The reason we still flag trigger phrases is that they correlate with the kind of email that filters distrust — shouty, link-dense, low-context. Treat the spam list as a writing-quality signal, not a magic blocklist, and your copy gets better even where deliverability was never at risk.
The highest-leverage field is the one people skip: preview text. Leave it blank and the inbox scrapes your first body line — often an image alt tag, a ‘view in browser’ link, or nothing. Filling it with a deliberate 40-90 character continuation of the subject is the cheapest open-rate lift in email, and it is the first fix we make on almost every account we inherit.
How it works
The tester runs a series of independent checks on your subject, preview and body, each carrying a weighted penalty, and subtracts them from a starting score of 100. Higher-impact problems (empty subject, heavy link ratio, ALL-CAPS) cost more than minor ones (missing personalization). The result is a 0-100 score plus a priority-ordered fix list.
- Subject length — ~30-50 chars shows in full on mobile; over ~60 truncates.
- Spam triggers — phrases like ‘free’, ‘act now’, ‘guaranteed’ that correlate with filtered mail.
- Preview text — the inbox snippet beside the subject; ~40-130 chars.
- Link-to-text ratio — too many links per word reads as spam to filters and people.
- Call-to-action — every campaign email needs one obvious next step.
Penalty weights are an RGM rule-of-thumb scoring model, not a vendor spam score. Authentication (SPF, DKIM, DMARC), sender reputation and recipient engagement drive real deliverability far more than copy — see Google’s sender guidelines. Always validate subject and preview choices with your own A/B tests.
Why the inbox preview is the real battleground
A subscriber sees three things before deciding to open: the from-name, the subject, and the preview snippet. That is the entire pitch. Everything else in the email — the design, the offer, the copy you labored over — only matters if those three lines earn the click. Optimizing them is the highest-return work in email, and it is almost free, which is why testing the subject and preview before every send is non-negotiable on the accounts we run.
Deliverability and engagement are now the same problem. Mailbox providers route mail partly on how recipients have engaged with you, so a clean, relevant, well-formatted email both lands better and performs better. The signals this tool flags — shouty subjects, link-dense bodies, missing CTAs — hurt on both fronts at once. Fixing them is not gaming a filter; it is writing the kind of email people actually open.
The catch is that none of these are guarantees. The 30-50 character subject window is a strong default, not a law, and some audiences reward a long, curiosity-driven subject or a single bold emoji. Use the score to remove obvious own-goals, then let A/B testing decide the judgment calls. A tester gets you to a clean baseline fast; your own data tells you where to break the rules.
Email copy rules of thumb
These are widely cited defaults, not hard limits — test them against your own list.
| Element | Common target | Why |
|---|---|---|
| Subject length | ~30-50 characters | Shows in full on most mobile clients |
| Preview text | ~40-130 characters | Fills the inbox snippet deliberately |
| Spam phrases | Zero | Correlate with filtered, low-context mail |
| Links in body | Few, with context | Link-dense copy reads as spam |