Definition
Email subject line examples are proven templates, formulas, and patterns that marketers use as starting points for writing effective subject lines. Rather than creating each subject line from scratch, successful email writers adapt tested formulas to their specific audience, offer, and campaign goals.
Subject lines are the single most important factor in email open rates. A strong subject line can double your open rate. A weak one means your email goes unread regardless of how good the content is.
Subject Line Formulas by Goal
| Goal | Formula | Example |
|---|---|---|
| Curiosity | [Intriguing statement] + [What?/Why?/How?] | "We ran 500 tests. Here is what surprised us" |
| Urgency | [Deadline] + [Offer] + [FOMO] | "24 hours left: your 30% discount expires" |
| Benefit | [Specific result] + [Timeframe] | "Increase open rates by 40% in 30 days" |
| Personalisation | [Name] + [Relevant content] | "Glenn, your email deliverability report is ready" |
| How-to | How to + [Desirable outcome] | "How to write subject lines that get opened" |
| Social proof | [Number] + [Social validation] | "Join 50,000 marketers who read this weekly" |
| Question | [Question that subscriber relates to] | "Struggling with low email engagement?" |
| Announcement | [What is new] + [Benefit] | "New: AI-powered send time optimisation" |
| Number/list | [Number] + [Topic] | "7 email mistakes costing you sales" |
| Teaser | [Hint] + [Curiosity gap] | "You won't believe what happened when we..." |
Subject Line Examples by Campaign Type
| Campaign Type | Example Subject Lines |
|---|---|
| Welcome | "Welcome to the list", "Your free guide is inside", "Glenn, here is what to expect" |
| Abandoned cart | "You left something behind", "Your cart is expiring", "Complete your purchase, Glenn" |
| Promotional | "30% off ends tonight", "New collection just dropped", "Members-only sale starts now" |
| Newsletter | "This week in email marketing", "5 things we learned this month", "Your weekly roundup" |
| Re-engagement | "We miss you, Glenn", "Is email still working for you?", "Come back for 20% off" |
| Event/webinar | "You are invited: [Webinar name]", "Saving your spot for [Event]", "Live in 1 hour" |
| Survey/feedback | "Tell us how we are doing", "5 minutes to improve your experience", "We want your opinion" |
Subject Line Length Benchmarks
| Length | Mobile Display | Open Rate Impact |
|---|---|---|
| 0-20 characters | 7-10 words visible | Highest short-term |
| 21-40 characters | 5-7 words visible | Most common sweet spot |
| 41-60 characters | 3-5 words visible | Reduced on mobile |
| 60+ characters | 2-3 words visible | Significantly truncated |
Most email experts recommend subject lines between 30-50 characters for optimal display across desktop and mobile.
Subject Line Do's and Don'ts
| Do | Dont |
|---|---|
| Personalise with subscriber name | Use ALL CAPS |
| Create curiosity without being misleading | Make false promises |
| Match the email content | Use excessive punctuation (!!!) |
| Test multiple variations | Rely on spam trigger words |
| Keep it scannable | Make it a complete sentence |
| Use numbers and specifics | Be vague or generic |
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Related Glossary Terms
A/B Testing
A/B testing in email marketing is the practice of sending two variations of an email to a small sample of your list to determine which version performs better before sending the winner to the remaining subscribers.
Abandoned Cart Email
An abandoned cart email is an automated message sent to customers who added items to their online shopping cart but left without completing the purchase. It is one of the highest-converting email types in ecommerce.
AI Content Detection
AI content detection refers to the growing ability of email clients, spam filters and consumers to identify machine-generated email copy. It matters for deliverability, trust and engagement in an era of mass-produced AI marketing email.
AI Email Summary
An AI email summary is a short, machine-generated overview of an email's key points, shown by Gmail, Outlook and Apple Mail before a recipient opens the message. It is reshaping how email marketers think about subject lines, preview text and open rates.
AI-Generated Content in Email
AI-generated content in email is copy, images, code or subject lines produced by artificial intelligence tools to speed up campaign production and testing.
AI Inbox Summary
An AI inbox summary is an AI-generated digest that condenses unread email — often highlighting news, actions and senders — changing how clearly your marketing email reaches and engages subscribers.
Frequently Asked Questions
A/B test at least 3-5 subject line variations for each major campaign. Test different angles, tones, and formulas to identify what resonates with your specific audience. Test continuously because subscriber preferences evolve.
Subject lines between 30-40 characters display best on mobile devices, where most opens now occur. Keep the most important words in the first 30 characters so they are visible without truncation.
Emoji use in subject lines is audience-dependent. Some audiences see emojis as friendly and modern. Others perceive them as unprofessional. Test emoji vs no-emoji variants for your specific audience. When using emojis, use a single relevant emoji near the end of the subject line.
Advanced personalisation includes location-based content, recent purchase or browsing behaviour, anniversary or milestone dates, segment or tier references, and previous engagement history. "Glenn, your London event is next week" outperforms "Glenn, an event near you."
The curiosity + benefit formula consistently performs across industries and campaign types. Combine an intriguing hook with a clear benefit: "How [Company] increased [Metric] by [Percentage]" or "The [Number] [Topic] strategies that actually work."