55% of responses to cold email campaigns come from a follow-up. It's essential that you send at least one if you want your prospects to reply.

To ensure your prospects open your follow-up emails in the first place, you need an engaging subject line.

In this article, we’ll show you can make the most out of follow-up subject lines in cold email campaigns. Test them out yourself to discover which ones resonate with your prospects and get you more replies to your cold emails.

  1. Does Your Follow-Up Email Subject Line Matter?

  2. 49 Follow-up Email Subject Line Examples to Get Your Emails Noticed

  3. Don't Forget to Optimize for the Opening Snippet of Your Email

  4. 5 Follow-Up Email Subject Line Best Practices

Let's jump in.

Does Your Follow-Up Email Subject Line Matter?

Some cold email experts say that subject lines don't matter.

There is some truth to that. As long as it doesn't come across as spammy and is at least a little bit personalized subject line relevant to the prospect, your email will probably get opened.

For most follow-ups, sticking with the same subject line is best, as you won't annoy your prospects by sending them emails in multiple email threads.

But, there is a time and a place to test a new subject line.

For example:

  • If your follow-up is on an entirely different topic to your initial emails

  • You've nearly sent your entire follow-up sequence and want to change the approach

Expert tip: Tracking your email open and reply rates can be good indicators of how effective your follow-up subject lines are. For this, you need a cold email software, such as QuickMail, where you can track the metrics. This is how the metrics look on QuickMail:

P.S. You can track open, click, reply, unsubscribe, and bounce rates with QuickMail! Get started with a free 14-day trial.

49 Follow-up Email Subject Line Examples to Get Your Emails Noticed

Next, we're going to show you real subject lines you can use in your follow-up emails. Make sure to tailor them to your exact business and prospect, and always remember to test different variations to find the best ones for you.

1. Ask a Question Immediately

Questions stimulate the recipient’s curiosity and invite them to open the email. As well as inciting curiosity, this framework is effective because it's hard to go wrong with it. Asking a 'quick question' isn't going to make you look overly pushy or give your prospect a bad first impression of you.

Here's a good example that RightInbox sent:

It's simple but still makes it clear why they're reaching out.

Here are eleven follow-up subject line examples you can use:

  • "Question"

  • "Quick question about [Pain Point]"

  • "Quick question, {{prospect.first_name}}"

  • "Another question, {{prospect.first_name}}"

  • "What do you think?"

  • "15 minutes of your time?"

  • "Can we talk on {{=day+2}}?"

  • "Interested in solving [pain point]?"

  • "Chat about {{company.name}}?"

  • "{{company.name}} + [Your Company]"

  • "Coffee, maybe?"

All of these subject lines are open-ended enough that your prospect will open them. You can also test these in lowercase.

2. Pay Your Prospect a Compliment

People love hearing other people praising them and their work. Because of that, paying your prospect a compliment in your subject line can work well to boost your open rate.

The key is that when you pay a compliment to your prospect, it should be genuine.

If you're making something up, it'll be obvious. For example, if you tell a prospect: "I love your podcast!" then go on to mention nothing about it in your email template, it'll be clear that you don't care much about their podcast. That's worse than not mentioning it at all.

After paying a compliment in your subject line, make sure to follow it up in your email. For example, if you told them you enjoyed their podcast, make sure to mention a specific detail about it in your email's opening line or in the P.S. at the end.

Here are six examples of how you can pay your prospect a compliment:

  • "Love [feature] in [prospect’s product]"

  • "Excited to try [prospect’s newly launched product]"

  • "Great seeing/meeting/listening/talking to you at [event/destination]"

  • "Watched your talk at [conference/event]"

  • "Read your article on [topic]"

  • "Enjoyed your podcast with [guest name]"

Showing you've looked into your prospect's business or content they've produced is the perfect way to show them that you're actively invested in starting a conversation and haven't just thrown them onto a generic email campaign with thousands of other people.

3. Be Direct and Promise Value

Being transparent about the reason for your email shows your prospects you're not here to waste their time.

Calling out the service you're offering or the pain point you're solving will almost guarantee that your prospect will open your email.

One consideration is that you need to make your subject line as specific as possible here. For example, if you want to help them with marketing, tell them the exact pain point you're reaching out to help with, like Facebook Ads, link building, or writing blog posts for them.

For example, RepurposeHouse directly mention the service they offer in this subject line:

Here are five examples of follow-up subject lines that provide

  • "Ideas on reducing your cost-per-lead"

  • "I’ve got some Facebook Ad ideas for you, {{prospect.first_name}}"

  • "Useful tactic to help {{company.name}} get results with SEO"

  • "Want to discuss {{company.name}}'s YouTube strategy?"

  • "3 ideas for {{company.name}}'s LinkedIn outreach strategy"

Subject lines like these show you're reaching out for a specific purpose. If your email lands in the inbox at the same time your prospect is thinking of how to solve that problem in their business, there's a strong chance it will lead to a conversation.

4. Keep Your Subject Line Simple and Non-Descriptive

In the previous set of examples, we looked at specific subject lines. But, you can also go the opposite direction and keep your follow-up subject line vague.

The idea is to only provide enough information to make your prospect curious enough to open your email.

For example, if you only mention your prospect's name or their company name in the subject line, they know that you’ve at least done some basic research into who you’re reaching out to. In most cases, that's enough motivation for someone to open an email.

The best thing about these minimalist and simple subject lines is that it forces you to avoid click-bait or sales-y phrases. Less information means less of a chance to go wrong.

Here are seven examples you can test out:

  • "[Empty subject line]"

  • "{{prospect.first_name}}"

  • "{{company.name}}"

  • "Question about {{company.name}}"

  • "Question for you"

  • "Quick question"

  • "Got 15 minutes?"

These subject lines are vague, but they're not misleading either. The worst-case scenario is that a prospect will think you're being too vague and open your email to find out what you're emailing about.

5. Making It Clear Who Is Emailing

If your first email wasn't opened or replied to by your prospect, introducing yourself in the subject line can be a good way to help them notice you in the inbox.

The benefit to this strategy is that everyone who opens your emails is clearly interested in hearing what you have to say, and it puts a name to the email, helping you stand out from the other sales emails in their inbox.

Here are five simple ways to introduce yourself in the subject line:

  • "Hello again from [your name / your company]"

  • "[Your company] –> {{company.name}}"

  • "[Your name] –> {{prospect.first_name}}"

  • "{{prospect.first_name}} and [Your company]: Potential collaboration?"

  • "{{company.name}} <> [Your Company]"

6. Mention a Mutual Connection, Interest, or Event

Following up after meeting someone at a networking event, or having something in common like living in the same city is a powerful way to follow up.

Where possible, use this in your opening email rather than waiting for a follow-up, but there's always a chance you learned that you had something in common after you'd already reached out.

It's nearly impossible to craft a more compelling subject line than one that shows your prospect how much you have in common with each other.

This type of subject line will make your cold emails warm and can hugely boost response rates as your recipient will know you haven't just downloaded their contact details from a random online contact database.

Here are five examples of this in practice:

  • "Met you at [conference/workshop/event]"

  • "Tech-founder to tech-founder"

  • "Coffee in Berlin this week?"

  • "Referred to you by [mutual friend]"

  • "[mutual friend] told me to reach out"

These work because the subject lines are specific and relatable for your prospect. If someone emailed you mentioning a conference you attended or the city you live in, you’d open it almost one-hundred percent of the time.

7. Add Urgency and FOMO

If your email sequence isn't being opened or replied to, then you can try adding urgency. If your prospect has been putting off answering you due to being busy with other projects, urgency can be an excellent way to grab their attention.

Here are five examples of urgency in follow-up subject lines:

  • "Last time I'll email you"

  • "Not interested in growing revenue this quarter?"

  • "You don't want to miss this"

  • "Final check-in"

  • "Is this the right email for {{prospect.first_name}}?

These subject lines won't resonate with everyone. But, they can work well near the end of a campaign if you're looking for a new way to engage with your prospect.

8. Use Humor, Wit, and Creativity

You're competing for attention in your prospects' inboxes. They're decision-makers, which means other cold emailers and SDRs are reaching out to them at the same time you are.

One way to make your follow-up stand out is to inject some humor.

Before using humor, make sure it fits the situation and industry you're operating in, as there's a risk of making you look unprofessional.

But, if your company culture and industry are okay with using humor in a business context, then it's worth testing.

For example, AppSumo makes a joke relating to dating apps in their subject line in this campaign. It's creative and helps their email stand out in the inbox.

Caveat: your humor is different from your prospect's sense of humor, so there's a risk of your emails being marked as spam if your recipient doesn't find your humor funny.

That said, here are five subject lines you can test to add some humor to the engagement:

  • "the most polite unsolicited note you’ll get today"

  • "Opening gambit attempt #[X]"

  • "the audacity of this email"

  • "Swipe right?"

  • "Don't open this email!"

Follow-up subject lines relying on humor and creativity won't always work, but they can be a fun way to change the tone of your interaction and show's your prospect that there's a real person behind the email.

If you use a funny subject line you’ll also need to continue with your tone in the rest of your email. It’ll look strange if you’ve tried to catch your prospects’ attention with humor and then switch back to a serious tone for the rest of your cold email.

Don't Forget to Optimize for the Opening Snippet of Your Email

If your prospect hasn't opened or replied to your previous emails then there may be more to it than just the subject line.

You need to consider the preview snippet of your email.

What is the snippet?

It's the bit of text from your email body that shows up next to your subject line in the inbox.

If your subject line isn't interesting, there's still a strong chance your snippet can.

To make sure it has a positive effect on your open and reply rates, use a personalized opening line in your emails, or add compelling content to the start of your follow-up emails.

Even if your prospect skips past your subject line, your snippet can be the key to getting your email opened and replied to.

5 Follow-Up Email Subject Line Best Practices

Writing a good follow-up subject line isn't rocket science. But, there are some best practices that will help you write good subject lines fast.

1. Keep It Simple and Relatable

The majority of advice, data, and studies on subject lines out there are related to traditional B2C email marketing.

Conventional marketing wisdom says you need to stand out, induce FOMO, and use catchy phrases to grab your recipient’s attention. Cold email campaigns run on different dynamics, and you can’t apply those principles here.

Imagine your friend sends you an email to inform you about a 45-minute yoga session. Wouldn’t you find it unusual if you see this subject line in her email invite: “I transformed my mind, body, and soul. You can too. For FREE!”? You probably wouldn’t even open it unless the email was from your friend.

On the other hand, if the subject line was something like: "Yoga this Saturday?", it's a lot more authentic and feels more personal.

The best follow-up subject lines for cold email campaigns work not because they stand out, but because they are conversational, natural, and relatable.

2. Focus on the Right Metrics

Optimizing for the wrong metrics can lead to problems. For example, if you were optimizing for open rates you'd see the best results using clickbait subject lines that trick people into opening your email.

But, even if you trick your prospects into opening your email, what do you achieve? There are no points for a high open-rate that doesn’t result in conversations or sales.

This doesn’t mean metrics like open rates are useless. A low open rate indicates low deliverability, an unqualified prospect list, underperforming subject lines, or all three. If your response rate dips, there might be issues with the email message.

But instead of experimenting with hundreds of subject lines and using a new one for every follow-up you send, spend your time focusing on building a highly qualified prospect list and writing email templates that get replies from your ideal prospects.

3. Keep Your Subject Line Short

Short subject lines allow the recipients to view your entire subject lines on all devices without risking part of it being cut off. Considering your prospects will be reading your email on mobile as well as desktop, it's essential.

Some studies suggest that subject lines that are four words or less produce the best results, while some claim that the sweet spot is between 6 and 10 words. Regardless of the exact number of words and characters, we recommend keeping your subject line length short enough to be easily read on mobile.

Or, as mentioned in our interview with Peep Laja, if you want to ensure your email always gets opened, you can try using one word, all lowercase, and possibly with a spelling mistake. You'll stand out, incite your recipient’s curiosity, and chances are, your email will get opened.

4. Always Add a Personal Touch

Personalized subject lines make your prospects feel that you crafted the email just for them.

If you received an email and it mentioned your name or your company name, you'd be more likely to open it and read the message with a positive mindset.

If you’re willing to put in extra effort, find and mention some mutual connections. Your prospect might be your fellow alumni, a professional in the same industry, live in the same area of your city, or be a fan of the same folk band.

Even if you don't want to bring up those things in the first email you send, it's an excellent way to make your follow-up subject line unique and eye-catching.

5. A/B Test Your Subject Lines

What works for someone else might not work for you and your niche. Always take examples like those we've provided with a grain of salt. For your unique business, something completely different might work best. Until you've found your follow-up subject line is consistently performing well, you can run A/B tests and experiment with variations.

Here’s how you can efficiently test your follow-up email subject lines:

  • Make a list of subject lines you want to test

  • Set up your A/B test so different prospects receive different subject lines (more on how to do this below).

  • Add at least 100 prospects into each test. If you test on fewer than that, your sample size won’t be large enough for a conclusive result.

  • Send your email campaigns and measure the results.

  • Find the subject lines that produce the best results, and double down on it. When assessing results, make sure you focus on the true metric that matters: conversations started with prospects.

  • Repeat the above steps whenever you want to test a new subject line idea.

You can easily A/B test your follow-up subject lines in QuickMail using Variations.

Add a new variation to your email step, and add the subject line you want to test.

When you launch your campaign, your two emails will be sent, and you'll see clear metrics on which one performs better.

However, don’t obsess over your subject lines in your follow-ups. It's better to quickly iterate rather than spending days or weeks coming up with the perfect subject lines. In most cases, all you need to do is avoid blatantly 'spammy' phrases and show some relevance to your prospect. Then, you'll be good to go.

Automating Your Follow-up Emails with QuickMail

If you're ready to launch your email campaign complete with a sequence of follow-ups, QuickMail can help you automate the whole process.

After writing your first cold email, you can choose the delay between your first and second email. Typically, 2-3 days is adequate. As your sequence goes on, you can extend the delay between emails.

Then, it's time to schedule your next email.

Add a new email step, and compose your email in the editor.

You can choose whether to keep your email in the same email thread, or whether or not to add a new subject line in your follow-up.

When you launch your campaign, you can track opens and replies for every email to find out which of your steps generates the most engagement.

When someone replies to one of your emails — whether it's the first cold email in your sequence or the fifth— the campaign will pause, so they're never sent an email they shouldn't receive.

Start your free trial of QuickMail today and start more conversations with your perfect prospects.