Simple rules for subject lines
- Lead with the benefit. I call it "lead with greed": what does the reader get?
- Be specific. Numbers and concrete nouns help.
- Keep it short. Many inboxes cut long subject lines on phones.
- Match the content. The FTC's CAN-SPAM guide prohibits deceptive subject lines.
Subject line examples by type
| Type | Example |
|---|---|
| Delivery | "Here's your free follow-up checklist" |
| How-to | "How to raise your prices without losing clients" |
| Number | "3 mistakes new guitar students make" |
| Question | "Are you charging enough?" |
| Story | "The giveaway that attracted the wrong people" |
| New video | "New video: the first line of your description" |
| Invitation | "Doors open: [offer] (details inside)" |
What should you avoid?
- ALL CAPS and stacks of exclamation points.
- Clickbait that the email doesn't deliver.
How do you test subject lines?
Most email services let you A/B test two subject lines. Because Apple Mail Privacy Protection can inflate opens, judge winners by clicks when you can (open rates explained).
Example
Worked example: rewriting weak subject lines
| Weak | Why it's weak | Stronger |
|---|---|---|
| "Newsletter #14" | Says nothing about what's inside | "The 3-minute fix for blurry YouTube videos" |
| "Quick question!!!" | Vague and spammy | "Which of these 2 offers would you pick?" |
| "You won't BELIEVE this" | Clickbait; damages trust | "What happened when I moved my link to line one" |
| "Big announcement" | About you, not them | "New: a free checklist for your next video" |
| "Hi" | Looks like a personal message, then disappoints | "Your welcome checklist (as promised)" |
The pattern: say what the reader gets, be specific, and keep the promise in the email itself.
A five-minute subject line routine
- Write the email first. The subject line should describe what's actually inside.
- Write five options using different angles: a benefit, a question, a number, a "how to," and a curiosity line that's still honest.
- Cut each to about 40 characters if you can, so it isn't cut off on phones. Put the key words first.
- Read the preview text (the first line people see after the subject). Make it add information, not repeat the subject or say "View in browser."
- Pick the plainest one that's still interesting. When unsure, choose clear over clever.
Subject line formulas that suit business emails
- "How to [result] without [pain]": "How to film at home without a studio"
- "[Number] [things] for [person]": "5 video ideas for local plumbers"
- "The [mistake] I see most": "The description mistake I see most"
- "[Name of video]: new video": works well when your list joined from YouTube
- "Re: your question about [topic]": only if someone actually asked
Watch out
Mistakes to avoid
- ALL CAPS and lots of exclamation marks. They look like spam to people and filters.
- Fake "Re:" or "Fwd:" on emails that aren't replies. It feels like a trick, and it is.
- Promising something the email doesn't deliver. Opens may rise once, then readers learn to ignore you.
- Changing your sender name. People decide whether to open based on who it's from as much as the subject. Pick one name and keep it.
Dave’s take
A principle I keep coming back to
"Lead with greed." (Dave)
Tell people what they get before you tell them where to go.
AI shortcut
How can AI speed this up?
AI tools and plans checked October 18, 2026. They change often, so confirm on each tool's own page. No affiliate links.
- Get options. Ask for ten subject lines; keep the plainest two.
- Casual voice. Grok is good at short, conversational variations.
Tools mentioned:
- ChatGPT: free plan, Go ($8 a month in the US) and Plus ($20 a month).
- Claude: free plan, Pro at $20 a month.
- Grok: free to start with limited use, works alongside X; paid plans start at Plus ($8 a month), with Premium at $30 a month.
AI is great for first drafts. Always edit the result so it sounds like you and is accurate for your business.
Key takeaways
- Say what's inside and lead with the benefit.
- Short and specific beats clever.
- Never mislead; US law requires subject lines that reflect the content.
- Test two versions and judge by clicks, not just opens.
