27 Follow-Up Email Subject Lines & Tips How to Write Them

27 Follow-Up Email Subject Lines & Tips How to Write Them

Follow-ups improve response rates significantly. As a research based on analysis of 12M cold emails showed, you can boost your reply rates by 65% by just sending a single follow-up.

At Hunter, we noticed the campaigns we are doing internally performed 38% better when they include a follow-up email.

Subject lines have a significant impact on the success of your cold outreach campaigns. Prospects decide whether to read your email or not based on subject line only.

In this guide, we gathered the most effective follow-up email subject line examples and tips on how to craft them. We also asked industry experts to share their best practices and examples with us.

If you don’t have time to read the whole guide, you can take this list of best-performing follow-up email subject lines with you to get fresh insights and examples right away.
1. Make a connection with the previous email
2. Keep it short and catchy
3. Make it personal
4. Ask open-ended questions
5. Avoid sounding passive-aggressive
Automate sending follow-ups
Best follow-up email subject lines tested by industry leaders

1. Make a connection with the previous email

When you think about adding follow-ups to your cold email campaigns, there are two key approaches you can take:

  1. Send follow-up in the same thread as an initial email;
  2. Send follow-up as a new message.

Each of these methods has its pros and cons. Before jumping into details, let’s have a quick overview of both approaches.

1. Send follow-up in the same thread as an initial email

At Hunter, we recommend using the same thread with the same subject line for your cold follow-up.

This way, prospects quickly get reminded about the offer from the previous email. Moreover, you can use follow-ups to continue telling the story, or offering additional benefits in this case.

Send emails in one thread

Just imagine sending the same follow-up as above as a new email: it would be probably hard for a cold prospect to remember the context of the first email and who you are.

Follow-up sent from the same thread would be part of the story you started telling from the first email.

Besides that, changing the subject line to create new threads might be perceived as slightly more aggressive, as they create multiple rows in most popular email clients.

For example, this is how follow-up with a new subject line looks in Gmail:

New emails view in Gmail

And here is an example from the Outlook:

New emails view in outlook

2. Send follow-up as a new message

However, there are some situations where using a new thread to follow-up might be relevant.

The typical use cases are:

  1. Your prospect doesn't open the first email, and you assume that it’s because the subject line wasn’t catchy/relevant.
  2. You want to test different subject lines for your follow-ups, and you know how to connect all of the previous messages in one story.
  3. You made a mistake in the initial email and noticed it before sending a follow-up. In this case, you have another opportunity to make the “first impression” once again.

If you want to send a follow-up email in a new thread because of one of these reasons, you need to understand that there's a chance that the recipient will probably not check the original email. So make sure to provide additional context from your initial email in the follow-up. You should expect the recipient to know enough to start the discussion from the follow-up sent in a new thread.

Follow-up connection

That would be another reason why for most of the cases we recommend using the same subject line for all your emails—you’ll not need to explain the reason why you contact your prospect every time in detail. When you have all of the follow-ups in the same thread, it’s easier to keep them short, catchy, and straight to the point.

However, if you have a decent reason to send a follow-up as a new email (because of the A/B test, to contact someone who didn’t open your previous email, etc.), you can follow these simple rules to write follow-up email subject lines that make prospects open your emails.


2. Keep it short and catchy

When writing a subject line for your follow-up email, try keeping it short and catchy.

It’s much easier to catch a prospect’s attention with something short, sweet, and straight to the point.

Just compare these two subject lines. Which one would you open?

  • Next steps with {{business}}
  • Let’s discuss with you the next steps and how to increase revenue for {{business}}

I bet the first one. People often open emails because of curiosity. Intriguing your prospect with a subject line is something you should consider for your follow-up campaign.

Another reason to keep your follow-up subject lines short is that long subject lines are cut off on mobile devices.

Cut-off subject line

Mobile email will account for 26 to 78% of email opens, depending on your product, target audience, and other criteria. You can’t just miss out on such a massive chunk of the email opens because your subject line is too long.

These are some of the examples of the short and catchy follow-up email subject lines:

  • Right person
  • Moving on
  • Ready for {{event}}?
  • Check this out, {{first_name}}
  • Congrats
You can get more fresh insights on subject lines for follow-ups on Hunter Templates. This is the most extensive directory of best-performing cold email templates, and subject lines tried and tested by industry experts.

3. Make it personal

Personalization is another crucial point for a successful follow-up email subject line. No one loves receiving generic “Hi there/Quick question” emails.

You should do your research before contacting prospects and get as much information on them as possible to make your outreach campaign successful.

To personalize subject lines for your follow-ups, you can start with something as simple as the prospect’s name and company, and go in-depth and add advanced personalization such as the place you’ve met, the content they wrote, etc.

Adding a personal touch to your follow-up subject line is your best bet to get high open rates. However, it’s not always doable for bigger volumes to edit all the emails manually since it could take a decent amount of time.

Fortunately, tools like Hunter Campaigns can help you save time preparing and scheduling highly-personalized emails.

Hunter Campaigns doesn’t “automate the whole process” but still saves hours of your time. It’s always better to spend a bit more time to add a personal touch to each message, even though they will be sent on autopilot.

1. Create a CSV file with detailed information about your prospects

Find information about your prospects and gather everything in a single CSV file.

CSV file with emails

2. Upload it into Hunter Leads

Hunter Leads is a simple CRM tool that allows you to structure information about your prospects and keep track of the results of your cold outreach.

If you use Hunter to find your prospects’ email addresses and their personal information, there is no need to create a CSV file—you can save this info directly to Leads.
Hunter Leads

3. Use custom attributes for subject line personalization

Custom attributes allow you to easily substitute personal information about your leads in your subject lines and emails. This is one of the simplest ways to automate your outreach and affect a personal touch at the same time.

Custom attributes for subject line

Here are a few great examples of personalized subject lines for follow-ups:

  • Your thoughts {{first_name}}?
  • {{first_name}}, I’m closing your file
  • I’ve been thinking of {{company}}
  • Congrats on {{event}}
  • Nice to meet you at {{event}}

4. Ask open-ended questions

Questions are a great way to focus your prospects’ attention on your message and pique their curiosity.

Questions also feel incomplete on their own, so they can inspire readers to open your email and search for an answer.

The questions you ask in your follow-up subject line may be ones that the prospect is already asking themselves. It could be related to the problem you shared in the first email or just something that you think can make your prospect curious.

Try to keep your questions open-ended so your prospect can’t answer them with a “no.”

These are a few examples:

  • What do you need at {{company}}?
  • Next step?
  • Have you thought of {{relevant_offer}}?
  • Your thoughts?
  • Why did you go?

5. Avoid sounding passive-aggressive

In your follow-up subject lines, avoid sounding passive-aggressive or desperate.

Here is an example that illustrates passive aggression without any further explanations:

Passive aggressive subject line

Direct aggression is relatively easy to spot, but more subtle passive-aggressive phrases can sneak into your follow-ups almost without thought. These kinds of microaggressions can exasperate your prospects and quickly chip away at the goodwill and mutual trust you have established.

With your follow-up subject lines, you should show confidence, provide additional value, and interest prospects with your offer, but definitely not come across aggressive or desperate.

Hence, try to omit such passive-aggressive phrases in subject lines for your follow-ups:

  • I’ve tried to reach you a few times now
  • I know you’re busy, I’m busy too
  • Any updates on this?
  • Just checking in
  • Friendly reminder

Besides that, try not to use the word “follow-up” in your subject line. It doesn’t provide any additional value to your prospect besides the information that you’re sending a “reminder” about the previous message that your prospect didn’t find attractive, skipped, or just didn’t have an opportunity to open.

Also, try to remove desperation from your follow-up subject lines. Yes, you might be upset because your prospect didn’t respond to your previous email, but don’t show them your distress.

These phrases are a proper signal you sound a bit desperate, so try to omit them as well:

  • If it’s not too much trouble
  • I apologize in advance for bothering you
  • Sorry for being so persistent

Automate sending follow-ups

You can easily automate the whole outreach process, including sending follow-ups with Hunter Campaigns—our free and simple cold outreach tool.

Once you add a copy of your initial email to Campaigns, choose when you want your follow-up to be sent.

Automate sending follow-ups 1

You can choose one of the suggested options: from 1 to 14 days, depending on your campaign and goals.

The next step would be to decide whether you want to send all follow-ups in the same thread as the initial email or for each of them to be sent as a new message with different subject lines.

Keep this field empty if you want to send a follow-up as a reply to your previous email:

Automate sending follow-ups 2

Or add a subject line to send as a new message:

Automate sending follow-ups 3

You can add up to three follow-ups to your initial message and customize the delay for each follow-up.

Once your follow-ups are sent, with Campaigns’ stats, you can measure the effectiveness of your follow-ups. You can track how many follow-ups were sent, opened, clicked, and replied to.

Automate sending follow-ups 4

Best follow-up email subject lines tested by industry leaders

We contacted a few industry leaders who do impressive cold outreach campaigns and asked them to share their best-performing cold follow-up subject lines with their open rate and thoughts on why such lines had great success.

Here is what they shared:

{{first_name:"Hey"}} I forgot to mention...

Open Rate: 84.95%

"I think that this follow-up subject line has great success because it has the prospect's name in the subject line. It is short and perks people's curiosity to wonder what was not mentioned. It also shows that I'm human and make mistakes, showing a more natural side to myself." - Shared Rachel Steinbauer, Head of Outbound Sales at Kinsta


Yet another candid (but hopeful) attempt at guest posting!

Open Rate: 45.72%

"I think this follow-up subject line has always worked well for us because it's short, to the point, and very clearly conveys the email's intention. It also attempts to humbly nudge the reader to open it without trying too hard." - Shared Tanishq Agarwal, Outreach Strategist at Beaconstac


[LIVE WEBINAR] Learn why 70-80% of your visitors aren’t buying

Open Rate: 21.43%

"This was a follow-up email we sent after an initial cold outreach email, inviting our mailing list to join a webinar on abandoned cart email practices. The reason this subject line performed well:

1) The focus was e-commerce centric, which we knew most of our subscribers would respond to, as they belong to the same domain, either as marketers, owners or researchers.

2) The subject line incorporated both curiosity ("learn why") and a compelling statistic ("70-80% of your visitors aren't buying") to make the subject line truly eye-catching and worth a click to find out what the email was actually about." - Shared Rukham Khan, Contend Lead at Mailmunch


A quick question {{first_name:"for you"}} 😉

Open Rate: 68%

"We run link building campaigns on a regular basis, and this follow-up subject line performed the best in the context of gathering new backlinks opportunities. In my opinion, it resulted in a high open rate due to the interest of what is behind such a topic. On some level, it has a psychological context as we, humans, are always curious and don’t want to miss that question/offer/deal." - Shared Andriy Zapisotskyi, Growth Manager at Mailtrap


[Reminder] Your Preferences Will Shape The Safe Re-opening Of Hospitality Venues

Open Rate: 35.68%

"This follow-up subject line was part of our survey campaign to understand the audience's preferences, inclinations, and hesitations about the future of the hospitality industry in a post-COVID-19 era.

It was a great success as the global event audience resonated with being a contributing factor in the bigger picture. The ownership of contributing and sharing their perspective anonymously made this a success." - Shared Siddharth Das, Content Marketer at Yapsody


❤️ what you do at {{company:"your company"}}

Open Rate: 82%

"This follow-up subject line worked because, first, it was personalized. It immediately connected with people and complimented them on their current work. The subject line is short enough to be read in its entirety, even on mobile devices. The subject line also created enough intrigue for people to read what's inside it. We naturally linked the email to their great work at their current role and asked them if they would like to do even greater work here at Recruiterflow." - Shared Ifrah Nasser, Content Marketing Manager at Recruiterflow


Here’s what I’ll do

Open Rate: 61%

"Link building emails these days are far too spammy, and they ask more than they give. People don't care about your blog post. Trust me. They care about the value they will get from you. Using this subject line imputes value, something they will get from opening and reading your email." - Shared Jeremy Moser, Co-Founder & CEO at uSERP


Additional resources

If you want to make a deeper dive into the subject lines & follow ups writing, I recommend checking these resources out:

Wrap up

Subject lines are one of the most important parts of your cold outreach. To make someone read your email, you need to make the person open it first. It’s even more challenging to persuade  someone you contacted before but with no success to open your email.

Following simple tips from this guide, you’ll be able to significantly increase your chances to get noticed and increase your open rates.

Have questions or feedback? Don’t hesitate to ping me on Twitter or drop a few lines at irina@hunter.io.

Irina Maltseva

Irina Maltseva

Head of Marketing at Hunter. I enjoy working on inbound and product marketing strategies. In spare time, I entertain my cat Persie and collect airline miles.

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