ChatGPT Prompt to Write High-Converting Email Subject Lines

0 views Updated Oct 21, 2026

This ChatGPT prompt for email subject lines is for marketers, founders, and anyone sending newsletters or campaign emails who wants more opens without resorting to clickbait that tanks trust or triggers spam filters. A subject line has one job: get the email opened, and that means it has to earn attention in a crowded inbox in under 60 characters while still being honest about what's inside.

The prompt below asks ChatGPT, Claude, or Gemini to generate a batch of subject line variations for a single email, each built around a different angle — curiosity, urgency, benefit-driven, personalization, or a direct/plain statement — so you can see several real options side by side instead of one guess. It also asks the model to flag any line that risks landing in spam (too many exclamation points, all caps, words like "free" or "guarantee" stacked together) so you're not shipping something that never reaches the inbox at all.

Subject lines are short, so small wording choices matter more than in almost any other piece of copy, and it's easy to end up with five variations that all sound the same. Once you've got a batch you like, running the strongest two or three through Compare & Diff can help you see exactly how they differ side by side before you commit to an A/B test.

Prompt template

prompt-template

284 tokens

ROLE: You are an email marketing copywriter who specializes in subject lines that get opened without feeling like clickbait. CONTEXT: Audience: [DESCRIBE YOUR AUDIENCE, e.g., existing customers, cold prospects, newsletter subscribers] Email summary: [SUMMARIZE WHAT THE EMAIL IS ABOUT OR PASTE THE BODY] Tone: [E.G., casual and friendly / professional / playful] Character limit: [E.G., 50 CHARACTERS MAX] TASK: Write 8 subject line options for this email, covering these distinct angles: 1. Curiosity (creates an information gap without being vague or misleading) 2. Clear benefit (states the value directly) 3. Urgency or timeliness (only if genuinely relevant to the content) 4. Personalization-style (implies relevance to the specific reader) 5. Plain, direct statement (no gimmick, just clearly says what's inside) Write at least one line for each angle above. CONSTRAINTS: - Stay within the character limit I specified. - Do not use ALL CAPS, excessive punctuation (!!!), or words that commonly trigger spam filters (free, guaranteed, act now, winner). - Each line must accurately reflect the email content — no misleading claims. OUTPUT FORMAT: A numbered list with the angle labeled before each subject line, followed by a one-line note on which 1-2 you'd recommend testing first and why.

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Example input

example-input

290 tokens

ROLE: You are an email marketing copywriter who specializes in subject lines that get opened without feeling like clickbait. CONTEXT: Audience: existing customers who signed up for our project management app's free tier 3+ months ago and haven't upgraded Email summary: We're announcing a new feature, automated weekly status reports, that's only available on the paid plan. The email explains what it does and includes a 14-day trial offer. Tone: casual and friendly Character limit: 50 characters max TASK: Write 8 subject line options for this email, covering these distinct angles: 1. Curiosity (creates an information gap without being vague or misleading) 2. Clear benefit (states the value directly) 3. Urgency or timeliness (only if genuinely relevant to the content) 4. Personalization-style (implies relevance to the specific reader) 5. Plain, direct statement (no gimmick, just clearly says what's inside) Write at least one line for each angle above. CONSTRAINTS: - Stay within the character limit I specified. - Do not use ALL CAPS, excessive punctuation (!!!), or words that commonly trigger spam filters (free, guaranteed, act now, winner). - Each line must accurately reflect the email content — no misleading claims. OUTPUT FORMAT: A numbered list with the angle labeled before each subject line, followed by a one-line note on which 1-2 you'd recommend testing first and why.

When to use it

You're sending a newsletter or campaign email and want several real subject line options instead of settling for the first one you think of
Your open rates have been flat or declining and you suspect subject line fatigue is part of the problem
You're A/B testing subject lines and need genuinely distinct variations, not five versions of the same phrase
You need to write a subject line fast under deadline and want a structured way to generate options rather than staring at a blank line

Best practices

Give the model the actual email body or a summary of it, not just a topic, so the subject line reflects what's really inside
Ask for subject lines built around different angles (curiosity, benefit, urgency, plain statement) rather than five variations on the same idea
Set a hard character limit (most inboxes truncate around 40-60 characters on mobile) so you're not writing lines that get cut off
Explicitly ask the model to flag anything that reads as spammy or clickbait-y, since those patterns can hurt both open rates and deliverability

Common mistakes

Asking for "catchy" subject lines with no other direction, which tends to produce generic clickbait that doesn't match the actual content
Not giving a character limit, so half the options get cut off on mobile before the key word appears
Overusing urgency or scarcity language in every line, which trains recipients to tune out your emails over time
Testing subject lines that are only cosmetically different (swap one adjective) instead of testing genuinely different angles

FAQs

How many subject lines should I test at once?

Two at a time is usually enough to get a clean read on which angle performs better; testing more than two or three simultaneously dilutes your sample size and makes results harder to trust unless your list is very large.

Why do my AI-generated subject lines all sound the same even when I ask for variety?

This usually happens when the prompt doesn't specify distinct angles. Explicitly asking for curiosity, benefit, urgency, and plain-statement versions, as separate categories, forces the model to actually vary its approach instead of rephrasing the same idea five times.

What words should I avoid in subject lines to stay out of spam folders?

Words like "free," "guaranteed," "act now," and "winner," especially stacked together or paired with excessive punctuation or all caps, are commonly flagged by spam filters. A single instance of one word rarely causes issues, but the combination and frequency matter.

What tool can help me compare which subject line option is actually stronger?

Compare & Diff — it lets you line up two prompt or copy variations side by side, which is useful for deciding between your top subject line candidates before running a live test.

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Claude Prompt to Draft a Tailored Upwork Proposal via MCP

This is a prompt for freelancers using Upwork's MCP server to draft tailored proposals directly inside Claude, ChatGPT, or Cursor instead of…

I'm applying to this Upwork job through your MCP connection. Here's the job post:

[PASTE FULL JOB POST TEXT HERE]

Here's relevant background from my profile/portfolio:
[YOUR RELEVANT SKILLS, PAST PROJECTS, OR RESULTS — BE SPECIFIC]

Write a proposal that:
1. Opens by referencing a specific detail or problem from the job post — not a generic greeting.
2. Connects one or two pieces of my real experience directly to what they're asking for.
3. Suggests a concrete first step or question that shows I've actually read the brief.
4. Closes with a clear, low-pressure call to action.
5. Stays under [WORD LIMIT] words.

Don't invent any experience I haven't listed above.

Content Creation & Copywriting

AI Prompt to Draft a Mailchimp Win-Back Email Campaign for Lapsed Subscribers via Mailchimp's MCP Server

This prompt drafts a Mailchimp win back email campaign aimed at lapsed subscribers, pulling the audience's actual engagement history through…

ROLE
You are an email marketer writing a win-back campaign for a segment of lapsed email subscribers.

CONTEXT
- Audience source: Mailchimp, accessed via the connected MCP server
- Segment name or ID: [SEGMENT_NAME_OR_ID]
- Inactivity window: [NUMBER] days since last open or click
- Offer or incentive, if any: [OFFER_DESCRIPTION_OR_NONE]
- Number of emails in the sequence: [NUMBER_OF_EMAILS]

TASK
1. Read the segment's recent engagement history and past campaign categories from the connected Mailchimp MCP server.
2. Identify the content or product categories this segment engaged with before going inactive.
3. Draft a sequence of the specified number of emails: each with a subject line, preview text, and body copy.
4. Make the final email in the sequence a clear "last chance" or list-cleanup notice.

CONSTRAINTS
- Do not guilt or shame the subscriber for being inactive.
- Reference the segment's actual past engagement categories; do not invent interests not supported by the data.
- Keep each email under 150 words of body copy.
- If no offer is specified, do not invent a discount or incentive.

OUTPUT FORMAT
## Segment Insight
[What this segment engaged with before going inactive]

## Email 1: [Purpose]
Subject: [Subject line]
Preview text: [Preview text]
Body: [Body copy]

## Email 2: [Purpose]
[Same structure, repeat for each email in the sequence]