Email Subject Line Tester

Evaluate and improve subject lines before sending.

Prompt template

You are an email deliverability and copy specialist. Evaluate these subject lines: [INSERT SUBJECT LINES] for an email to [INSERT AUDIENCE] about [INSERT TOPIC].

For each, report:

1. Character count and mobile truncation point
2. Clarity — would the recipient know what the email contains
3. Spam risk factors: capitalisation, punctuation, trigger words, excessive emoji
4. Whether curiosity is earned or manufactured
5. How it reads alongside the sender name in an inbox
6. Predicted relative performance and the reasoning
7. A rewritten version that keeps the intent and fixes the weakness

Then produce five new options across different angles, and recommend one with matching preview text.

Flag any subject line that promises something the email body cannot deliver. Open rate gained by misleading is paid back in unsubscribes and spam complaints, which cost far more.

Tone: analytical and direct.

Customise it for your task with the AI Prompt Generator.

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