Man writing follow up email subject line on devices

Nearly half of your email recipients are likely to open your emails based only on your subject line. And most of your responses come from follow-up emails.

This should be enough to convince you about the absolute importance of subject lines in follow-up emails — until you read the next stat.

Emails without subject lines have an average 8% higher open rate than those with subject lines.

If the subject lines are so important, why is their absence more effective?

In this article, we’ll disrupt some conventional wisdom related to subject lines and discuss how you can make the most out of follow-up subject lines in cold email campaigns.

5 Follow-up Email Subject Lines Best Practices

Person reviewing follow up email subject lines on tablet

Subject lines are not as important as people believe. The fact that their absence is more effective reveals how poorly marketers use them.

A large number of recipients indeed open their emails based on the subject line, but that doesn’t mean you have to complicate cold email subject lines. Statistically, subject lines don’t affect the open rates much as long as they’re not spammy. However, here are a few tips for writing a good subject line.

1. Keep It Simple and Relatable

The majority of advice, data, and studies on subject lines 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.

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

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

Cold email discussions center around open and response rates, which can be misleading. It’s easy to achieve higher open rates through deception and high response rates consisting of negative replies.

This doesn’t mean these metrics are useless. A low open rate indicates low deliverability, underperforming subject lines, or both. If your response rate dips, there might be issues with the email message.

3. Keep It Short

Short subject lines allow the recipients to view subject lines completely on all devices. Trends show thatmore than half of the email recipients first open their emails on their mobile devices.

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. We recommend testing subject lines lengths shorter than 50 characters and picking the ones that perform the best.

Or, as mentioned in our interview with Peep Laja, ideally use one word, all lowercase and possibly with a spelling mistak 🙂

4. Add a Personal Touch

Personalized subject lines make your prospects feel that you crafted the email just for them. They’re then more likely to open your email and read the message with a positive mindset. You can use either your recipient’s name or their company’s name in the subject.

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.

5. Test Your Subject Lines

What works for someone else might not work for you and your niche. When you ditch conventional wisdom, trial and error is the best way to move forward. Even if your current follow-up subject line is performing well, it doesn’t mean it can’t do better. The only way to know this is to test.

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

  • Make a list of suitable cold email subject lines.
  • Divide your cold email follow-up campaign into multiple parts, each with a different subject line, while keeping everything else constant.
  • Feed at least 100 prospects into each campaign. If you feed fewer leads, the sample size won’t be large enough for a conclusive result.
  • Run the campaigns and measure the results.
  • Pick the subject lines that produce the best results. Make sure you also consider conversion, response, unsubscription, and click-through rates along with open rates to evaluate the results.
  • Repeat the above steps with new subject line ideas.

But as mentioned, don’t obsess over subject lines. Just avoid spammy things.

Common Follow-up Email Mistakes To Avoid

Woman crouching behind laptop

It’s difficult to follow up, especially after your prospects ignore your first attempt to connect. We compiled a list of the most common mistakes of following-up so you can make your follow-up emails even better than the initial email.

  • You follow up too often: If you follow-up every day, you’ll come across as desperate. Your emails will be sent to the spam folder more often. Space out the follow-up emails by at least three days.
  • You follow up too late: It’s easy for your prospects to forget you if you take too long to follow up on your initial sales email. Best follow-up practices recommend reaching out to your prospects within a week.
  • You follow up after a “No”: Several salespeople are instructed to keep pushing to a certain extent even after the prospect is not interested. It’s not only unethical but also impacts your deliverability, as you’ll often receive a higher spam score.
  • You don’t personalize your follow-up email message: You don’t need to write separate emails for each prospect. But if you spend a couple of minutes on their LinkedIn profiles or their company’s social media, you can add a personalized sentence to your email copy. Econsultancy research found that nearly three-fourth of the marketers say that personalized emails result in higher engagement rates. This significantly boosts your engagement.

Follow-up Email Subject Line Examples

Hands holding illustrated envelope in front of pink background

Here are some ideas you can include in your cold email follow-up subject lines, demonstrated by effective follow-up email templates:


Questions are loose ends. They stimulate the recipient’s curiosity and invite them to open the email.

  • Question
  • Quick question
  • Quick question, {{prospect.first_name}}
  • Another question, {{prospect.first_name}}
  • What do you think?
  • 15 minutes of your time?
  • Can we talk tomorrow?
  • Are you still interested?
  • Can we chat about [prospect’s product, service, or company]?
  • {{}} + [YourCompany]


People love hearing good things about them and their work. If you truly believe something good about your prospect or their company, you can include a compliment. Make sure your compliment is genuine. Your prospects will easily know if you’re using flattery to sell your product or service.

  • Love [product feature] in [prospect’s product]
  • Excited to try [prospect’s newly launched product]
  • Great seeing/meeting/listening/talking to you at [event/destination]


Offering value to your prospects is a way of conveying that you want to help them. If your value attempts to solve their pain points, they will likely open your email.

  • {{prospect.first_name}}, want some ideas on [service you’re pitching – for example: reducing cost-per-lead?]
  • I’ve got some [your discipline] ideas for you, {{prospect.first_name}}
  • Free tactics to help {{prospect.first_name}} get [your discipline] results
  • Want to discuss [prospect’s pain point]?


Cold email subject lines that are not descriptive can produce excellent results. The idea is to provide little to no information in your follow-up email subject lines.

For example, if you only mention the name of the prospect or their company in the subject line, they know that it’s about them. But they don’t know what it’s about. It provokes them to open the email.

The best thing about being vague is you can avoid click-bait or salesy phrases. Less information means less of a chance to go wrong.

  • Remove the subject line
  • Use Emojis to convey emotion
  • {{prospect.first_name}}
  • {{}}

Humor, Wit, and Creativity

Busy business professionals receive hundreds of emails each week from marketers like you. Why should they choose you over others?

Using humor, wit, and creativity in your cold email campaigns serves two purposes: You separate yourself from others by breaking the pattern, and you only work with people and companies that share the same values and are not uptight.

A witty subject line gets along with a humor-themed cold email campaign. Caveat: Humor and creativity are highly subjective, and as such have a much higher chance of getting marked as spam, so use these at your discretion (or later in the campaign to get a reply).

  • cajolement attempt #X
  • Don’t make me come over there…
  • Blatant Clickbait (at least, they get what they expected)
  • u ok?
  • the most polite unsolicited note you’ll get today 🙂
  • Opening gambit attempt #[X]
  • the audacity of this email


Not many things can go wrong with a simple introduction. But if you didn’t introduce yourself in the first email, you can do it in one of the follow-up emails.

  • Hello again from {your name / your company}
  • [Your company] –> {{}}
  • [Your name] –> {{prospect.first_name}}

Mutual Connections

Addressing common connections can make your cold emails a bit warmer and can massively boost your open and response rates. The prospects feel that you are reaching out to them from a reference rather than from a random list.

  • Met you at [X summit/conclave/workshop/event]
  • Tech-founder to tech-founder

Automate Your Follow-up Emails

With the right automation, you can set trigger points that send different follow-up sequences for different user actions in the previous email. By default, the follow-up stops when the recipient replies or unsubscribes.

Sending individual emails, following up, personalizing, and testing for the best email subject lines can be a tedious and time-consuming process.

Fortunately, cold email platforms like QuickMail come to your rescue by automating most of the repetitive tasks. Besides automation, these tools enable lead management and campaign optimization through flexible sending volume, email frequency, sending times, and gaps between follow-up emails.