‍21 Killer Cold Email Subject Lines (91% Open Rates)

Ever wondered why your cold emails aren't getting the attention they deserve? Well, the secret often lies in something as simple as the subject line. Crafting the best email subject lines can skyrocket your open rates and set the stage for a successful email outreach.

In this article, we’ll share 21 killer cold email subject lines that boast an impressive 90% open rate.

Here’s what we’ll cover:

• Proven strategies: Discover the secrets to crafting compelling subject lines.
• High-performing attention grabbing subject lines: Get inspired by subject lines with top open rates.
• Best practices: Learn how to boost your email open rates consistently.
• Personalization tips: Find out how to make your subject lines more engaging.

P.S., The best cold email subject line in the world still won't work if you're not reaching out to the right customer for your business. If you're tired of wasting time finding the right buyers, cleaning spreadsheets, and verifying their emails and phone numbers, try ListKit to build your first triple-verified lead list of high-potential buyers so ALL your emails land – and turn into a sale.

TL;DR - The Best Cold Email Subject Lines

• Strategies for Crafting the Best Subject Line: Effective subject lines leverage psychological triggers like curiosity, urgency, and personalization to maximize engagement.
• Best Practices for High Open Rates: Keep subject lines short and engaging, use numbers and questions to grab attention, and personalize where possible to increase relevance and interest.
• The Best Cold Email Subject Lines (we break each down in sections below):
  • "Quick question"
  • "Are you struggling with [pain point]?"
  • "How [company] can boost your [specific metric]"
  • "Here's a solution to your [problem]"
  • "Can we help with [specific issue]?"
  • "Quick win for [recipient’s company]"
  • "Let's chat about [relevant topic]"
  • "Your competitors are using [product/service]"
  • "3 strategies to improve [specific metric]"
  • "Can you handle more [leads/customers/etc.]?"
  • "Quick 5-minute chat about [topic]?"
  • "Are you ready for [upcoming event]?"
  • "Increase your [metric] by X% in Y days"
  • "question about {company}"
  • "question for {name}"
  • "{name} + YOUR NAME"
  • "{company} + YOUR COMPANY"
  • "open to connecting, {name}?"
  • "looking for XYZ? (insert your service)"
  • "Got 5 minutes {name}?"
  • "{name}, an observation about {company}"
  • "Open to a quick call {name}?"
• Personalization Techniques: Tailoring subject lines to include personal details like the recipient's name or specific interests can make emails feel more personalized and boost engagement.
• Continuous Improvement and Testing: Regularly test different subject lines and analyze their performance to continually refine strategies and improve open rates.

Why a Good Subject Line Matters

• Sets the Tone: A compelling cold email subject line does more than merely get your email opened; it establishes the tone and context for everything that follows.
• Drives Engagement: It can ignite curiosity, create urgency, or offer a tantalizing glimpse of the value waiting inside the email.
• Impacts Open Rates: Effective subject lines are crucial; they have a significant impact on your open rates. A strong subject line ensures that your valuable content gets the attention it deserves.

Psychological Triggers in a Great Subject Line

When you write subject lines for cold emailing, using psychological triggers like curiosity, urgency, scarcity, and personalization can dramatically improve your open rates. By crafting compelling subject lines that incorporate these elements, you can start sending successful cold emails instead of junk mail that turn into sales.

Key Strategies for Effective Email Subject Lines:

1. Curiosity:

• What It Does: Creates a sense of intrigue, significantly increasing open rates.
• Example: "Can You Handle More [leads/customers/etc.]?"
• Impact: Leveraging curiosity can lead to a 30% increase in open rates (HubSpot).

2. Urgency and Scarcity:

• What They Do: Compel readers to act immediately.
• Example: "Are You Ready for [upcoming event]?"
• Effectiveness: Urgent language increases open rates by 22% (MarketingProfs).

3. Personalization:

• What It Does: Makes recipients feel uniquely valued, boosting engagement.
• Example: "John, an observation about [company]"
• Statistics: Personalized subject lines can increase open rates by 29% (Experian).

Sales Email Subject Lines

1. "Quick question"

Why This Subject Line Works: Avoids a pitch right off the bat and is designed to spark a harmless conversation that you can turn into a sale.

When to Use: When you know a specific question will capture curiosity and lead the prospect down a certain questioning funnel.

Sample email starter with this subject line:

Hey [Name], are you using Klaviyo for email marketing?

2. "Are you struggling with [pain point]?"

Why This Subject Line Works: Directly addresses a common pain point, showing empathy and understanding.

When to Use: When you have identified a significant pain point the recipient is likely experiencing.

Sample email starter with this subject line:

Hey [Name], are you struggling with [pain point]? We helped a client overcome this exact challenge and improved their process efficiency by 30%. Open to a quick chat about how we can help you too?

3. "How [company] can boost your [specific metric]"

Why This Subject Line Works: Shows a clear benefit of your product or service, highlighting a specific metric to make the value proposition tangible.

When to Use: When you can offer a measurable improvement in a specific area.

Sample email starter with this subject line:

Hey [Name], we helped [Company] boost their [specific metric] by 25%. I’d love to share how we did it and discuss how we can do the same for you. Interested?

4. "Here's a solution to your [problem]"

Why This Subject Line Works: Offers a solution to a known issue, sparking interest and positioning your email as helpful and relevant.

When to Use: When you can provide a direct solution to a problem the recipient is facing.

Sample email starter with this subject line:

Hey [Name], here’s a solution to your [problem]. We implemented this for a client and increased their productivity by 30%. Open to hearing how we can help you too?

5. "Can we help with [specific issue]?"

Why This Subject Line Works: Engages the recipient by posing a question related to a problem they may have, inviting a response.

When to Use: When you know the recipient might have a specific issue that you can address.

Sample email starter with this subject line:

Hey [Name], can we help with your [specific issue]? We recently helped a client with a similar problem and reduced their downtime by 40%. Interested in seeing how we can help you too?

6. "Quick win for [recipient’s company]"

Why This Subject Line Works: Promises a quick and easy benefit, piquing curiosity and interest.

When to Use: When you can offer a fast and effective solution to a problem.

Sample email starter with this subject line:

Hey [Name], we have a quick win for [Company]. We implemented a similar strategy for a client and saw a 15% increase in sales within a month. Open to chatting about how we can do the same for you?

7. "Let's chat about [relevant topic]"

Why This Subject Line Works: Invites a conversation on a topic of mutual interest, building rapport and establishing common ground.

When to Use: When you have identified a relevant topic that is of interest to both.

Sample email starter with this subject line:

I noticed your interest in [topic]. We recently helped a client optimize their [related process], resulting in a 25% efficiency boost. I’d love to discuss how we can achieve similar results for you. Free next week for a quick call?

8. "Your competitors are using [product/service]"

Why This Subject Line Works: Creates a sense of urgency and competitiveness, motivating the recipient to take action.

When to Use: When you have information about industry trends or competitor activities that can benefit the recipient.

Sample email starter with this subject line:

Did you know that many of your competitors are already using [product/service] to improve their [specific area]? We helped XYZ Corp increase their productivity by 30% using this solution. Interested in hearing how we can do the same for you?

9. "3 strategies to improve [specific metric]"

Why This Subject Line Works: Offers actionable insights and specific numbers that capture attention and add value.

When to Use: When you have identified key strategies that can benefit the recipient.

Sample email starter with this subject line:

Here are three proven strategies to boost your [specific metric]: 1. Personalize your outreach, 2. Use data-driven insights, 3. Optimize your follow-ups. We helped a client increase their conversion rate by 20% using these methods. Open to learning how we can do the same for you?

10. "Can you handle more [leads/customers/etc.]?"

Why This Subject Line Works: Challenges the recipient and implies potential growth, positioning your offer as a solution for scaling.

When to Use: When you can offer a solution that addresses growth challenges.

Sample email starter with this subject line:

If you’re ready to scale, we can help manage your growing customer base. We recently helped a client double their lead volume in 60 days. Open to chatting about how we can support your growth?

11. "Quick 5-minute chat about [topic]?"

Why This Subject Line Works: Emphasizes a minimal time investment, reducing resistance to the call.

When to Use: When you need to propose a brief and focused discussion.

Sample email starter with this subject line:

I promise to keep it brief. Let’s discuss how we can improve your [specific area] with minimal time investment. We helped a client boost their ROI by 20% in just a month. Free for a 5-minute chat this week?

12. "Are you ready for [upcoming event]?"

Why This Subject Line Works: Ties your message to a relevant event, creating urgency and relevance.

When to Use: When an upcoming event or deadline is approaching.

Sample email starter with this subject line:

With [upcoming event] around the corner, are you prepared? We helped a client maximize their sales during the last event season, resulting in a 25% increase. Open to hearing how we can do the same for you?

13. "Increase your [metric] by X% in Y days"

Why This Subject Line Works: Presents a specific and compelling benefit, making the value proposition tangible.

When to Use: When you can provide concrete results within a specific timeframe.

Sample email starter with this subject line:

Our methods can increase your [metric] by 20% in just 30 days. We helped a client achieve this exact result last quarter. Interested in how we can do the same for you?

14. "question about {company}"

Why This Subject Line Works: Shows interest and personalization by directly addressing the recipient’s company.

When to Use: When you have a specific question related to the recipient’s company.

Sample email starter with this subject line:

Is {company} using Klaviyo for email marketing?

Networking/Connection Subject Lines (That Can Turn Into a Sale)

When you send marketing emails, they don't always have to be a sales pitch. A cold sales email can start with a request to just connect and get to know your target audience. This can give you higher response rates because people know yoi're not a sales rep trying to take their money.

Then, once you've established a relationship, you can spark a prospect's curiosity about something you offer. The advantage of networking first is you can make more offer more appealing, now that you have more information about the prospect's interest at hand.

1. "question for {name}"

Why This Works: Personalizes the email, sparking curiosity with a direct address.

When to Use: When you have a specific question that is relevant to the recipient.

Sample email starter with this subject line:

Hey {name}, are you currently using HubSpot for your CRM?

2. "{name} + YOUR NAME"

Why This Works: Personalizes the email, making it feel more like a personal connection.

When to Use: When you want to create a sense of familiarity and connection.

Sample email starter with this subject line:

Hey {name}, it’s [your name] here. I’d love to discuss how we can collaborate on [specific topic]. Can we set up a quick call?

3. "{company} + YOUR COMPANY"

Why This Works: Creates a direct connection between the two companies, making the email feel more relevant.

When to Use: When you want to emphasize the potential partnership between the companies.

Sample email starter with this subject line:

Hey {name}, I see that {company} is doing great work in [industry]. At [your company], we have some ideas on how we can collaborate to achieve even more. Interested in discussing this further?

4. "open to connecting, {name}?"

Why This Works: Directly asks for a connection, making it clear and straightforward.

When to Use: When you want to establish a connection with the recipient.

Sample email starter with this subject line:

Hey {name}, I’d love to connect and discuss how we can support each other’s goals. Open to a quick chat?

Service Offering Email Subject Line Examples

1. "looking for XYZ? (insert your service)"

Why This Works: Directly addresses a potential need, making the email highly relevant.

When to Use: When you know the recipient might be looking for a specific service.

Sample email starter with this subject line:

Hey {name}, are you looking for [service]? We’ve helped several clients achieve [specific result] with our services. Open to chatting about how we can do the same for you?

2. "Got 5 minutes {name}?"

Why This Works: Emphasizes a minimal time investment, making it easier for the recipient to agree.

When to Use: When you need to propose a brief and focused discussion.

Sample email starter with this subject line:

Hey {name}, do you have 5 minutes to discuss [specific topic]? I promise to keep it brief and valuable. Free for a quick chat?

3. "{name}, an observation about {company}"

Why This Works: Personalizes the email with an observation, showing that you’ve done your research.

When to Use: When you have a specific observation about the recipient’s company.

Sample email starter with this subject line:

Hey {name}, I noticed [something interesting] about {company}’s recent project on [specific topic]. Open to discussing this further?

4. "Open to a quick call {name}?"

Why This Works: Directly asks for a call, making it clear and straightforward.

When to Use: When you want to establish a connection and have a conversation.

Sample email starter with this subject line:

Hey {name}, I’d love to have a quick call to discuss [specific topic]. Are you free for a call this week?

Common Subject Line Mistakes to Avoid

Mistake: Using Spam-Trigger Words
Avoid spam-trigger words like “Sale,” “Earn,” “$$,” “Income,” and “Profit.” These words can trigger spam filters and land your email in the junk folder.
Do Right: Place your offer in the email body. Focus on creating subject lines that are clear and relevant to the recipient's interests.

Mistake: Failing to Optimize for Mobile
Not optimizing subject lines for mobile devices can reduce open rates, especially since 42% of emails are opened on mobile.
Do Right: Keep your subject lines concise—aim for 4-7 words or a maximum of 60 characters to ensure readability on smaller screens.

Mistake: Writing Generic Subject Lines
Generic subject lines fail to capture attention and can be easily overlooked.
Do Right: Be specific and pique curiosity with intriguing content that speaks directly to the recipient’s interests.

Mistake: Lack of Preheader Text
Neglecting to add preheader text misses an opportunity to provide additional context and entice the reader to open the email.
Do Right: Use preheader text to complement your subject line and provide a brief preview of the email content.

Mistake: Over-Personalizing Subject Lines
Overloading subject lines with too many personalization points can seem forced and inauthentic.
Do Right: Personalize smartly by using one or two key personalization points that feel natural and relevant to the recipient.

Deliverability and Achieving 90%+ Open Rates

When it comes to cold email outreach, deliverability is crucial. Even the best-crafted subject lines won't matter if your emails aren't landing in your recipients' inboxes. Here are some key strategies to ensure high deliverability and achieve open rates of 90% or more:

1. Authenticate Your Emails: SPF, DKIM, and DMARC - Set up these authentication protocols to verify that your emails are sent from legitimate sources. This helps prevent your emails from being marked as spam.

2. Maintain a Clean Email List: Regularly clean your email list to remove invalid, inactive, and duplicate email addresses. This reduces bounce rates and increases deliverability.

3. Warm Up Your Email Account: If you're using a new email account, start with a small volume of emails and gradually increase it. This helps build your sender reputation with email providers.

4. Monitor Your Sender Reputation: Use tools like Sender Score or Google Postmaster to monitor your sender reputation. A good reputation ensures better deliverability.

5. Avoid Spammy Words: Words like "free," "buy now," and "discount" can trigger spam filters. Focus on creating relevant and engaging content that resonates with your audience.

6. Personalize Your Emails: Personalization goes beyond using the recipient's name. Tailor the content to their specific needs and interests to increase engagement and reduce the likelihood of being marked as spam.

7. Use a Reliable Email Sending Service: Use reputable email sending services that have strong relationships with ISPs and ensure high deliverability rates.

8. Regularly Test and Optimize: Continuously test different subject lines and email content to see what works best. Use the data to optimize future email campaigns.

9. Engage with Your Audience: Encourage recipients to respond to your emails. Engaged recipients are less likely to mark your emails as spam.

Cold email sending tools like Smartlead lets you auto warm-up your cold email domains and A/B test your cold emails and subject lines.

By implementing these strategies, you can significantly improve your email deliverability and achieve open rates of 90% or more. Remember, the foundation of a successful cold email campaign lies not only in compelling subject lines but also in ensuring that your emails reach your audience's inbox.

How to A/B Test Your Subject Lines

Smartlead is a cold email sending software that provides robust tools for A/B testing your email subject lines, allowing you to optimize your cold email campaigns effectively.

1. A/B Testing Feature: Smartlead has built-in A/B testing capabilities specifically designed for cold email campaigns. You can create different versions of your subject lines and track their performance. This helps you determine which subject lines yield higher open rates and engagement.
2. Email Previews: Before sending out your campaign, use Smartlead’s email preview feature to see how your emails will look in your recipients' inboxes. This ensures that your emails are visually appealing and free of errors.
3. Integration with ListKit: To maximize the effectiveness of your A/B tests, import your highly targeted leads from ListKit into Smartlead. This integration ensures that your emails land in the inbox of potential high-quality leads, providing accurate and meaningful data for your A/B tests.

Close Your Next Lead With These Subject Lines Using ListKit

Wrapping up, you now have the tools and insights to craft compelling cold email subject lines. Your emails are on the path to achieving higher open rates and engagement. Here are the key takeaways from this article:

• Understand the Importance: Effective subject lines set the tone for your email.
• Leverage Psychological Triggers: Use curiosity, urgency, and personalization.
• Analyze Top Performers: Learn from the best subject lines.
• Customize Your Approach: Tailor subject lines to your audience, especially when referencing a mutual connection.
• Test and Optimize: Continuously improve based on data.

With these strategies, you're ready to transform your email outreach. To streamline your lead generation and ensure your email lists are top-notch, ListKit is here to help.

ListKit offers a vast database of triple-verified leads, ensuring your efforts are focused on high-quality prospects. This integration with Smartlead not only enhances the effectiveness of your subject lines but also ensures your emails land in the inbox of the right people.