B2B Cold Email Subject Lines That Convert

Are you a cold emailing professional looking to increase the chances of your emails being opened by 82%? You’re in the right place.

In 2024, our team analyzed the subject lines of over 5,000 cold email campaigns to uncover what makes or breaks success.

Now, in 2025, it’s time to share everything we’ve discovered. Certain subject lines stand out and make all the difference in achieving an 82% open rate.

Which ones? Let’s break it all down for you.

6 Tips for Crafting B2B Cold Email Subject Lines

This section is for the creatives out there. Want to learn the magic formula for writing your own compelling cold email subject lines? Here are our 6 best tips.

Tip 1: Write a Short and Powerful Subject Line

Keep it under 8 words and place the most impactful words at the beginning.

Our analysis has shown that open rates decrease as subject lines get longer. 

The longer the subject line, the less likely the email is to be opened. There are two key reasons for this:

1️⃣ Reason 1: Readers are overwhelmed by an endless stream of emails. A concise subject line of 8 words or less increases your chances of being opened by 91%.

2️⃣ Reason 2: 70% of internet users now check emails on their mobile devices, not on their computers. A subject line that isn’t optimized for mobile will appear truncated, reducing its impact.

Tip 2: Truly Personalize Your Subject Line to Grab Attention

Personalization means using relevant keywords. Here are two methods:

✅ Incorporate dynamic variables tailored to the prospect, such as:

• Their pain point: {{painPoint}}

• Their main competitor: {{competitor}}

• A shared connection: {{commonGround}}

• An important priority: {{Objective}}

Examples:

“How to solve {{painPoint}} in 30 days?”

“Outperform {{competitor}} with this proven strategy.”

✅ Leverage triggers:

• Shared content

• Recent achievements

• Notable updates

Examples:

“Your thoughts on your latest publication?”

“Congratulations on X!”

❌ What not to do:

Avoid basic personalization like “you” or {{firstname}}. Our analysis of thousands of campaigns shows that this approach has minimal impact on open rates.

Tip 3: Ask a Relevant Question

You read that right: a question can work, but only if it’s relevant. There are two ways to achieve this:

1️⃣ The question addresses the prospect’s specific pain point.

Example: “Do you need help with {{painPoint}}?”

2️⃣ The question surprises the prospect.

Example: “Are you really satisfied with a 60% open rate?”

In short, it’s not the use of a question mark that matters, but rather the level of personalization and relevance in your question.

Our analysis shows that generic questions don’t improve open rates. Worse, overusing question marks can harm your email’s performance and lower your open rate significantly.

Tip 4: Keep It Simple

Never forget that your reader’s time is precious. Simplify your writing as much as possible.

You’re not addressing the President of the United States. Your subject line doesn’t need to be overly formal. Keep it simple, casual, and to the point.

Our analysis clearly shows that simplicity works. In fact, this single factor can increase the open rate of a B2B email by 8%.

Tip 5: Create a Sense of Urgency or Emotion

Here’s how to do it:

👉 Offer exclusive deals.

Example: “A special gift just for you, {{firstname}}.”

👉 Leverage FOMO (Fear of Missing Out).

Example: “Last chance to join the event of the year, {{firstname}}.”

Caution: If this technique is misused, it can backfire. A poorly written subject line might get flagged as spam.

To avoid this, pay close attention to the format:

• Avoid writing your entire subject line in all caps.

• Be cautious with excessive emojis.

• Use only one exclamation mark. Adding more makes you look unprofessional.

Tip 6: Run A/B Tests on Your Cold Email Subject Lines

An A/B test helps identify which subject line generates the highest open rate, what truly grabs your audience’s attention, and how to optimize your B2B cold email campaigns.

Our Best Tips for a Successful A/B Test:

• Test one variable at a time (tone, length, dynamic variables, etc.).

• Use a representative sample: Divide your audience into two equal, random groups that reflect your target demographics.

• Track clear KPIs to measure performance.

• Run tests simultaneously: Send both versions at the same time to minimize the impact of external factors like timing or day of the week.

• Analyze results objectively: Don’t overinterpret small differences. Look for significant trends.

Examples of Relevant KPIs by Variable:

10 B2B Cold Email Subject Lines That Convert

This section is for those who need ready-to-use examples.

Here are our top 10 subject lines guaranteed to achieve an 82% open rate, drawn from our analysis of over 5,000 B2B cold email campaigns.

Subject Line 1: I Loved Your [X]!

⚙️ Why It Works:

• Shows genuine interest in the prospect.

• Casual tone that feels approachable.

• Maximum personalization.

• Focuses on the prospect first before mentioning your product.

⌚ When to Use It:

Perfect for a first contact. Keep an eye out for moments when your prospect publishes articles, videos, or relevant content.

🌟 Variations:

“I loved your article on Ideas for Christmas Marketing!”

“Thanks for your content on Gmail!”

Subject Line 2: Last Call {{firstname}}... Closing Soon

⚙️ Why It Works:

• Creates a sense of urgency

• Direct and casual tone, encouraging immediate action.

⌚ When to Use It:

Use this for offers or events with an imminent deadline. Perfect for re-engaging a prospect you’ve previously contacted.

🌟 Variations:

“Last day to take advantage of this offer, {{firstname}}!”

“X is closing soon! Are you ready, {{firstname}}?”

“Last call, {{firstname}}.”

Subject Line 3: A Little Surprise for You, {{firstName}}!

⚙️ Why It Works:

• Sparks curiosity

• Friendly and engaging tone, well-suited for a B2B audience.

• Promises a direct benefit to the prospect.

⌚ When to Use It:

When you’re confident the offer matches your prospect’s needs. Ideal for rewarding prospects after an interaction or encouraging initial engagement.

🌟 Variations:

“A special gift just for you, {{firstName}}!”

“Here’s a little surprise for you, {{firstName}}!”

“I’m so happy to share this with you…”

Subject Line 4: Collaboration With – {{Domain}}

⚙️ Why It Works:

• Captures the attention of B2B decision-makers.

• Direct tone that immediately conveys relevance.

• Shows the email is specifically tailored to this prospect.

⌚ When to Use It:

Only when targeting a specific prospect within a relevant Domain or sector. Ensure you can include social proof in your message. Perfect for professional networks like LinkedIn.

🌟 Variations:

“Let’s work together in {{Domain}}!”

“{{Domain}}: How about a collaboration?”

“Ready to collaborate on {{Domain}}?”

“A partnership idea for {{Domain}}.”

Subject Line 5: {{firstName}}, How About a Quick Chat?

⚙️ Why It Works:

• Personal and friendly tone.

• Light and casual, making it inviting to open.

⌚ When to Use It:

Particularly effective for one-on-one exchanges or exploratory outreach in B2B.

🌟 Variations:

“{{firstName}}, do you have a moment to connect?”

“A quick chat, {{firstName}}?”

Subject Line 6: X Ideas for {{painPoint}}

⚙️ Why It Works:

• Addresses the prospect’s specific problem.

• The numbered format (# ideas) promises structured, easy-to-digest content.

⌚ When to Use It:

Use when prior research on the prospect has revealed a specific need. Ideal for an educational approach where you offer added value before initiating a collaboration.

🌟 Variations:

“3 concrete ideas to solve {{painPoint}}.”

“5 solutions to overcome {{painPoint}} quickly.”

Subject Line 7: A Question About Company Culture

⚙️ Why It Works:

• Demonstrates genuine interest in the prospect.

• Doesn’t come across as a sales pitch.

⌚ When to Use It:

Perfect for starting a dialogue with decision-makers.

🌟 Variations:

“What are your core values at [Mail Merge for Gmail]?”

“How does [Mail Merge for Gmail] combine free features with efficiency?”

Subject Line 8: Ideas and Feedback for You and Your Business

⚙️ Why It Works:

• Companies value constructive feedback to improve their offerings.

• Positions your email as an enriching interaction rather than a simple sales pitch.

⌚ When to Use It:

Use when your analysis of {{companyname}} can lead to actionable suggestions.

🌟 Variations:

“A few suggestions for {{companyname}}.”

“Helpful ideas for {{companyname}}.”

“Enhance {{companyname}} with these insights.”

Subject Line 9: Hey {{firstName}}, Congrats on Your Funding Round

⚙️ Why It Works:

• Shows you’re actively following the prospect’s news.

• Builds an emotional connection by acknowledging their success.

⌚ When to Use It:

Perfect for starting a conversation. This requires precise and up-to-date research.

🌟 Variations:

“Congrats on your recent funding round, {{firstName}}!”

“Kudos on this big achievement, {{firstName}}!”

Subject line 10 : Build {{companyName}} like {{commonInterest}}

⚙️ Why It Works:

• Leverages FOMO (Fear of Missing Out) to create urgency.

• Precisely targets the prospect.

• Highlights a shared interest or aspiration between you and the prospect.

⌚ When to Use It:

Use when you’ve identified a specific ambition or a company model that {{companyName}} might want to emulate. Perfect for industries where success stories inspire decision-making.

🌟 Variations:

“Develop {{companyName}} as a leader in {{commonInterest}}.”

“Transform {{companyName}} into an innovation model in {{commonInterest}}.”

Top 5 Subject Lines to Absolutely Avoid

Now that you understand how to craft an effective subject line and why, let’s look at the 5 subject lines you should absolutely avoid.

Our analysis of over 5,000 cold email campaigns revealed their disastrous impact on your prospects!

⬇️ “❌ Your Content Will Disappear in 72 Hours!”

Why to avoid it: Spammy, overly dramatic, scary emoji. It focuses on clickbait rather than value.

⬇️ “Grab Your 30% Discount Now!”

Why to avoid it: Feels like a scam and lacks specificity. What is the discount for? Why should the prospect care?

⬇️ “Revolutionize Your Business with Blockchain Solutions!”

Why to avoid it: doesn’t address a specific need of the recipient.

⬇️ “ Most Companies Can’t Attract Top Talent. Here’s Why.”

Why to avoid it: Reads like a blog post title, not a helpful email. Lacks a direct, actionable benefit for the recipient.

⬇️ “Don’t Miss Out {{firstName}}! Time is Running Out!”

Why to avoid it: Overused urgency tactics, and words like “Don’t miss out” often trigger spam filters.

The Expert’s Take: How to Keep Your Emails Out of Spam

If you use Mail Merge for Gmail for mail merge campaigns, each email is sent directly from your Gmail account, making it less likely to be flagged as spam.

Here’s the top 20 words or phrases frequently flagged as suspicious by spam filters, especially when they appear in excess, in all caps, or are accompanied by too many emojis or exclamation marks.

Urgency or Scarcity Words:

• Limited Time!

• Act now

• About to expire

Rewards or Gains Expressions:

• Congratulations!

• Win ! Click now

• You’re a winner

Free Offers:

• 100% Free

• No cost

• No fees

• Get started free

Financial or Commercial Promises:

• Make money

• Get paid

• Increase sales

• Work from home

Ambiguous or Suspicious Expressions:

• Not spam

• Join millions

• Satisfaction guaranteed

• Unlimited

• Claim

• Call now.

Top Email Subject That Converted In 2025

Our analysis has clearly confirmed the trends for 2025.

This will be the year of cold emailing! Personalization, relevance, and emotion are the key ingredients.

Here are the subject lines that can exceed an 82% open rate:

“How to solve {{painPoint}} quickly, {{firstname}}?”

Incorporate relevant variables to show you understand your prospect’s specific needs.

“An idea to help {{companyName}} today.”

Prospects prefer honest and personalized approaches without overpromising.

“Your solution in 3 steps, {{firstname}}.”

Clear and concise subject lines continue to perform well, especially on mobile.

“I loved your [X]!”

Show genuine interest in your prospect’s activities. Make it about them!

Conclusion

You now understand the importance of a winning subject line. But in cold emailing, no detail should be left to chance. This is why it’s also crucial to start your email properly.

To help you further, we’ve created a comprehensive guide with templates to craft prospecting emails that convert.

And of course, for a high-performing mail merge tool, Mail Merge for Gmail is always here for you.