Best practices for subject lines

Your cold email subject line is your first (and sometimes only) chance to grab attention.

Your subject line is the first impression your email makes - and in cold outreach, it can mean the difference between an open and the trash folder. If you want to boost your open rates and get more responses, mastering subject lines is non-negotiable.

Here are four best practices to help you craft subject lines that get noticed:

PS. You can also use our AI Subject Line Generator to get 5 subject line ideas based on your cold email copy 😉🪄 Easy peasy!

1. Keep it short and sweet

Less is more when it comes to subject lines. Research shows that subject lines between 1-8 words perform best, with 1-2 word subject lines achieving the highest reply rates. Why?

• People scan their inbox quickly, and shorter subject lines stand out.

• Mobile devices often cut off long subject lines, so keeping it brief is crucial.

• Short, punchy lines create intrigue and encourage the recipient to open.

💡 Example: Instead of writing "Excited to Connect About Your Marketing Needs!" try "Quick question" or "Today" - concise and to the point.

2. Personalize your approach

Generic subject lines feel like spam. The more relevant your subject line is to the recipient, the more likely they are to engage.

Beyond just inserting their name, think about:

• Mentioning their company, role, or a recent achievement.

• Referencing a shared connection or event.

• Tying into their pain points or industry trends.

💡 Example: Instead of "Let's Talk About Your Business", try "About your recent post John" or "Congrats on the funding - quick idea for you" - making it feel like a warm, thoughtful message.

3. Avoid clickbait and false prefixes

Tricking recipients into opening an email might work once, but it destroys trust. Using misleading tactics like "Re:" (when it's not a reply) or "Fwd:" (when it’s not a forward) can get your email flagged as deceptive.

Other subject line mistakes that turn people off:

• Over-promising: "Game-changing solution inside!" (but it’s just a pitch).

• Bait-and-switch: "You won!" (but it’s just a sales email).

• Overuse of urgency: "Last chance!" (when there’s no real deadline).

💡 Example: Be honest and upfront. Instead of "Quick fix for [problem]" (which feels like clickbait), try "About [problem]" - it’s still intriguing but feels more genuine.

4. Test and Iterate

Even the best subject line strategies aren’t one-size-fits-all. What works in one industry or audience might not work in another. That’s why A/B testing is crucial.

To optimize your subject lines:

• Test different lengths (short vs. medium).

• Experiment with casual vs. formal tones.

• Try first-person vs. third-person framing.

• Analyze reply rates and tweak accordingly.

💡 Example: If you’re unsure whether a direct or curiosity-driven subject line works best, test:
A) "Curious about [challenge]"
B) "Using [tool or product]?"
C) "Updates on [topic, industry etc.]"

Track which one gets the best engagement and refine your approach accordingly. By keeping it short, personalizing it, avoiding gimmicks, and testing consistently, you can dramatically improve your reply rates.