Tools Free · Everyday marketing
Test your subject line.
Score a subject line, preview it in a desktop and mobile inbox, and scan the email for words that push it toward spam.
Inbox preview
- Length35 characters is in the sweet spot (30 to 50).
- Words8 words. Easy to scan.
- MobileFits on mobile without being cut (about 40 characters).
- Spam wordsNo common spam trigger words.
- PersonalUses a personalisation token.
Lengths count it as a short first name. Set a fallback so nobody sees "Hi ,".
- HookUses a question or a number, which adds curiosity.
- PreviewPreview text set (54 characters). 40 to 90 shows well on most clients.
Body scan
| Word or phrase | Type | Count |
|---|---|---|
| 100% free | Money | 1 |
| click here | Urgency | 1 |
| no obligation | Too good | 1 |
Hi {{first_name}}, I put together three PR ideas for your Q4 launch. Two of them take under an hour to set up. The audit is 100% free and there is no obligation. Click here to grab a slot before Friday. Maya
Spam words are one signal. Sender reputation and SPF, DKIM and DMARC matter more.
Get new tools first
Optional. New free tools and growth notes, roughly once a month.
How to use it
- Type your subject line and preview text.
- Paste the email body to scan it for spam words.
- Fix the flagged items and check the inbox preview.
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Questions founders ask
What is the best length for an email subject line?
Aim for 30 to 50 characters, or about 4 to 9 words. Mobile inboxes often show only the first 35 to 40 characters, so put the key words first. Short subject lines are easier to scan and less likely to be cut.
Do spam trigger words still matter in 2026?
Less than they used to. Gmail and Outlook rely mostly on sender reputation, authentication (SPF, DKIM, DMARC) and engagement. Heavy use of phrases like "free money" or "act now" can still add risk, and it lowers trust with readers.
Should I use emoji in subject lines?
One relevant emoji can help a subject stand out, especially for consumer brands. More than one tends to look promotional, and some clients render them poorly. Never let an emoji replace the actual message.