Email spam checker & subject line tester
Paste your subject line, preheader and email. See spam trigger words highlighted, shouting and link problems flagged, and how it looks in the inbox, with a fix for each issue.
- Free, no signup
- 248 trigger phrases
- Live as you type
- Runs in your browser
Your email
Checked in your browser. Nothing is sent or stored.
Inbox view
Only used for the inbox preview.
Around 30–50 characters is a common guideline. Past about 60, most inboxes cut it off.
Email type
Onboarding, re-engagement and trial emails. Usually treated as commercial, so include an unsubscribe link.
Tags are stripped before the copy is checked; images and links are counted from the HTML. Merge tags like {{first_name}}, %FIRSTNAME% and *|FNAME|* are recognized.
Paste a subject line to start
Results update as you type. Or load a deliberately spammy example to see what gets flagged.
A copy check, not an inbox placement test. Sender reputation and authentication matter most — check yours with the SPF, DKIM & DMARC checker.
Spam word & subject line checker in 3 steps
- 1
Paste your email
Subject line, preheader and body, as plain text or HTML. Pick marketing, lifecycle or transactional.
- 2
See what stands out
Trigger phrases are highlighted by severity, and every check shows what it found and why it matters.
- 3
Rewrite and re-check
Use the suggested alternatives, watch the copy score update as you type, and export the findings as CSV.
What the checker looks at
Patterns that make readers ignore, delete or report an email, checked the moment you type.
Trigger phrases by severity
248 phrases in six categories, matched as whole words, each marked mild, moderate or strong, with a better alternative.
Subject line length
Characters and words, with a length bar marking the common 50 and 60 character guidelines.
Shouting and punctuation
All-caps words (common acronyms like API and CRM are ignored), stacked exclamation marks, $$$ and emoji overload.
Preheader checks
Missing, too short, too long, or repeating the subject line.
Links, images and HTML
Link count, public URL shorteners and image-heavy emails. HTML is detected and stripped automatically.
Unsubscribe and address
Checks for an unsubscribe link and a postal address, based on the email type you choose.
What actually decides whether email lands in spam
A spam word checker can't predict inbox placement, and any tool that promises to is overselling. Gmail, Outlook and Yahoo decide where your email goes mostly from signals that have nothing to do with the words in it.
1. Reputation, authentication and engagement come first
- Authentication. SPF, DKIM and DMARC prove the email really comes from your domain. Gmail and Yahoo require all three from bulk senders. Check yours with the SPF, DKIM & DMARC checker.
- Complaints. Google asks bulk senders to keep the spam rate reported in Postmaster Tools below 0.3%, and ideally under 0.1%. Every "Report spam" click counts against you.
- Engagement. Opens, replies and moving mail out of spam tell filters people want your email. Ignored email slowly drags reputation down.
- List hygiene. Sending to old, bought or unconfirmed addresses causes bounces and spam-trap hits. Remove addresses that bounce and people who haven't engaged in months.
2. Why words still matter
Words are a weak signal for filters, but a strong one for people. A subject that says "URGENT!!! You've been selected" looks like a scam, so readers delete or report it, and those complaints hurt your reputation more than any single word. Plain, specific copy earns opens, and opens are the engagement filters reward.
3. Subject lines for SaaS lifecycle email
Lifecycle emails work when they're specific to what the user did. Say what's inside and why it matters to them now.
| Moment | Weak | Better |
|---|---|---|
| Not activated | Don't miss out!!! | Your workspace is ready. Connect your first data source |
| Trial ending | LAST CHANCE: act now | Your trial ends Friday. Here's what you've set up |
| Inactive | We miss you 😢😢😢 | 3 new signups since you last logged in |
| Failed payment | FINAL NOTICE: account suspended | Your card was declined. Update it to keep your data |
Keep it to around 30–50 characters, front-load the important words, use sentence case, one exclamation mark at most, and one emoji at most. Only use "RE:" or "FWD:" on genuine replies; the FTC's CAN-SPAM guidance says subject lines must not mislead readers.
4. Preheader tips
The preheader is your second subject line. Use it to add the detail the subject leaves out, not to repeat it. Aim for about 40–110 characters. If you skip it, inboxes show the first text in the email, which is often "View in browser" or an image's alt text.
5. Common trigger phrases and what to say instead
| Instead of | Try |
|---|---|
| Act now / Urgent | The real reason and date: "Your trial ends Friday" |
| Click here | Descriptive link text: "Open your dashboard" |
| 100% free | "Free plan, no card required" |
| Guaranteed | The actual terms: "Full refund within 30 days" |
| Congratulations, you've been selected | What happened: "Your first report is ready" |
| Dear friend / Dear customer | Their first name, or just "Hi" |
| Don't delete this email | A subject worth opening on its own |
| No risk / No strings attached | "Cancel any time" |
6. Don't forget the footer
Marketing email needs a visible unsubscribe link and one-click unsubscribe headers (List-Unsubscribe and List-Unsubscribe-Post), which your email provider adds. CAN-SPAM also requires a valid postal address in commercial email and that you honor opt-outs within 10 business days. Receipts, password resets and other transactional email are exempt from the unsubscribe requirement as long as they stay non-promotional.
Will this tell me if my email lands in spam?
No, and no copy checker can. Gmail, Outlook and Yahoo decide placement mainly from your sender reputation, authentication (SPF, DKIM and DMARC) and how recipients engage with your mail. This tool checks your copy for patterns that commonly hurt trust, open rates and complaint rates. To check authentication, use the free SPF, DKIM & DMARC checker.
Do spam trigger words still matter?
Less than they used to. Modern filters don't block an email because it says "free". But scam-style wording, shouting and fake urgency make people ignore, delete or report your email, and those reactions do affect your reputation. That's why most words here are marked mild and only scam-style phrases are marked strong.
How is the copy score calculated?
It starts at 100. Each check that needs fixing takes off 8–40 points, each improvement takes off 2–8, and notes and passes take off nothing. Flagged phrases take off 1 (mild), 3 (moderate) or 6 (strong) points, doubled in the subject and 1.5 times in the preheader, with at most 45 points lost to phrases.
How long should an email subject line be?
Around 30–50 characters is a common guideline. Most desktop inboxes show about 60 characters and phones often show fewer, so put the important words first and move detail into the preheader.
What is a preheader and how long should it be?
The preheader is the preview text inboxes show after the subject line. Aim for about 40–110 characters. If you leave it out, inboxes show the first text in your email, which is often "View in browser" or a stray link.
Do I need an unsubscribe link in every email?
In marketing email, yes. Gmail and Yahoo require bulk senders to support one-click unsubscribe on marketing mail and to show a visible unsubscribe link, and CAN-SPAM requires a working opt-out and a postal address in commercial email. Transactional email, like receipts and password resets, is exempt.
Why are link shorteners like bit.ly flagged?
Public shorteners hide where a link goes, and spammers use them heavily, so filters and readers treat them with suspicion. Link to your own domain and use UTM parameters or your email provider's click tracking instead.
Is my email content stored anywhere?
No. Every check runs in your browser. Your subject line, preheader and body are never sent to a server.
Keep going
The best spam filter fix is a relevant email.
Atlis tracks what users do after signup and sends lifecycle emails automatically when they matter: onboarding nudges when someone stalls, re-engagement when they go quiet, and failed-payment emails through Stripe or Paddle. Every email includes an unsubscribe link and one-click unsubscribe headers.
Free plan · No credit card · 10-minute setup