How to write killer email subject lines?

Published by Amandine on June 27, 2022 5/5 (121 votes)

How to write killer email subject lines?
14 min

Don’t know what to put in your email subject lines?

Did you know that deliverability is half of the work needed to achieve an open rate above 90%?

The rest comes down to choosing the right one for the channel, your target and the context.😉 Without the right recipe, your emails, no matter how well delivered, are likely to fall into oblivion for lack of sufficient interest from your audience…In this article, we are about to share our secrets to finding the best possible objects for your emailing campaigns.

This article was written in partnership with Scalezia. Scalezia assists startups, scales-up but also SMEs in implementing the latest growth methods to create sustainable growth , boost  ROI  and internalize these skills, in order to make the company autonomous in the long term.

They also offer a colossal range of free content, covering all the important topics of acquisition but also content creation, Product Market Fit research and many other topics essential to grow a business. 🎯 To access the courses, it’s here (you won’t regret it).

1. What are email subject lines?

Before starting the work of writing, it is necessary to understand the role played by the subject. And it would be no small thing to recognize that there are many misunderstandings about the email subject. No, its function is not to generate a conversion. No, it is absolutely not, either, to give visibility to your brand or your website. In fact, it is no less effective than those using a structure and a tone of voice marketing.

  1. To start with, think back to the last ten emails you opened: what is the ratio between emails sent by individuals (colleagues, relatives, partners) and legal entities (companies via newsletters and other transactional emails).
  2. What were the subject lines of the emails you received from individuals?

It is very likely that this ratio is very strongly in favor of the latter, and that the objects of said emails combine conciseness, abstraction and informality. We will come back to these points later. You opened thee-mailing for two reasons. Firstly, they were sent to you by individuals and not companies. Companies towards which you have, in an era where overexposure to marketing and advertising is constant, developed protection filters that help you sort out, or even ignore, commercial solicitations. Secondly, the short, abstract and good subject lines have made you curious enough to open the email and read its content. What important information can be hidden behind this laconic short-subject “Follow-up file”?

This brings us to the very function (and above all: the one and only one) of the object: to create curiosity in order to generate an opening.

debut de l'article sur l'objet mail

2. What should the subject line be for an e-mail?

Over time, our brain has built up filters that allow it to quickly analyze and filter emails received from a minimal amount of information. Keep them all : personalized emails, spammy…

Thus, a simple reading of the different subject lines and the sender is enough to determine the degree of urgency and priority of the content. As a result, your subject headline is able to categorize your email into three mental “folders”:

  • 1. Polluting emails or promotional content marketing, which bring nothing and cost more than they bring.
  • 2. Non-urgent emails, to be consulted later “when we have time” (i.e. never in 90% of cases).
  • 3. Urgent emails, to be consulted right away in order not to miss an important information. You want to open it Now.

It is crucial to fall into the third tactic : creating a sense of urgency or the fear of missing out an important message.

To do this, you need to empathize with the other person’s way of thinking about their emails. Every professional checks his or her inbox for a simple reason: to get information that will allow him or her to get ahead of the tasks at hand. Whether it’s to work more efficiently by coordinating with colleagues, to identify new opportunities that will allow them to gain value within their company, or to learn about important information that needs to be addressed urgently in order to avoid potential problems that they could have prevented (and thus avoid getting their fingers slapped).

Thus, for each email, a recipient will govern his decision making with the following question:

Of the elements available, is this email likely to help me in my work? Can I find something in it that will help me achieve my goals, or is it information that will harm me if I don’t read it right away?

Yes, and the email will be read.

No, and the email will at best be ignored, at worst deleted or marked as spam. The key is to produce a subject line that suggests either urgency or opportunity. The key here is the idea of suggestion. We will try at all costs to avoid anxiety-provoking objects and other false promises in order to establish a healthy relationship and a high level of interpersonal trust. The idea is to play on the abstraction of the object in order to let the recipient’s imagination do the rest of the work.

As you can see, producing an object is not a matter of chance and is the result of thinking about the aspirations and behavior of your audience. Two words: personalization and segmentation.

A well-mastered and intelligent play on their fears and aspirations is a particularly effective way to get them to open and read the email with interest and attention. However, be careful not to overdo it.

For example, avoid too explicit objects such as “URGENT”, which may cause an understandable annoyance to your audience.

3. What to write in an email subject?

The purpose of the subject line for your email marketing is not to sell, convince or persuade. The content of your email (once it is opened), the quality of your supporting materials and your sales skills will be much more likely to achieve this.

To answer this, let’s take a few lines to talk about copywriting, or the art of writing to entice your reader to perform a specific action, whether it’s a sale, a registration, a donation, or any other action leading to a more advanced relationship.

This discipline, as rich as it is complex, is governed by a multitude of psychological mechanisms and writing models, also called frameworks.

Of the most commonly used (and most effective) frameworks, the most notorious is AIDA, which consists of a sequential alignment of elements that seek to :

  • A: To attract the reader’s attention in order to make him interrupt his current activity to consume the rest of the content – we will try to answer the question “what’s in it for me”. 
  • I: Create Interest by bringing a specific issue, which we will try to make as palpable as possible so that the reader feels as concerned and emotionally involved as possible – we will try to answer the questions “what is the issue at stake?” and “am I concerned by this issue?”
  • D: Make the reader want to solve the problem by proposing a solution to the problem described – question: “How can I solve this problem in a safe, profitable, quick, effective and healthy way?
  • A: Finally, invite the reader to perform a specific Action that will allow him/her to obtain the said solution – question: “what should I do to obtain the solution presented quickly?”

Attention. Interest. Desire. Action (adding call to action). In that order. A formula so effective that it is found in the vast majority of persuasive and personalize writing. So now you know: the subject line of a marketing e-mail has no other function than to attract the recipient’s attention, so that he or she interrupts the Inbox Zero session to read the rest of the message.

Also, if you want to Use the AIDA Model for your automated marketing campaigns, check out this. 👇

4. Writing an effective emailing subject line

But then, why do you prefer short, abstract and non-marketing-sounding subject lines? A classic email box is made up of 3 main types of content:

  1. Solicited marketing emails (newsletters, transactionalemails…): these are emails that the recipient expects to receive and knows the sender
  2. Unsolicited marketing emails, which generally have little impact, and often end up as spam, for the simple reason that their reception goes hand in hand with the unpleasant feeling of being part of a mass of recipients stuck in a mailing list.
  3. Interpersonal emails, exchanged from one individual to another, which go hand in hand with the feeling that the interlocutor has taken the time to write the email received, to us and to us alone.

It is in this last category that you are looking to place yourself. And, if you look closely, these are usually introduced by again short, abstract and informal objects. So, of the thousands of objects we’ve tested over the past few years, the ones that work best on our end (across personas and industries) are:

  • Email 1: “Intro
  • Email 2 : ” Re: question “
  • Email 3 : ” Follow-up
  • Email 4 : ” (no subject) “

Each one generates 70% opens on average. At the scale of a campaign, it is therefore almost inevitable to reach 80% or even 90% of openings for your best email, provided that your deliverability is optimal. You have seen it: the above objects do not make any promises. There is no more deleterious practice than that of overselling the ins and outs of an interaction. Avoid at all costs trying to stand out with “clickbait” objects that risk misleading your audience and will cut short the trust relationship you are trying to build.

The possibilities are endless and it is crucial that you find objects adapted to your targeting and the context of the contact. For example, if your contact is about your contact’s website, you can test objects such as “Site {company}”, “Question {domain}” or simply “Site” with your target.

In the same idea, if you send a good email reminder consisting of a high value-added video, you can simply use “video”. These choices emulate the way any time-sensitive individual introduces emails: with speed, simplicity and disinterest. “(no subject line)” is an example taken to the extreme.

rapidité de lecture gif

As you can see, the objective here is twofold. On the one hand, it is to arouse the recipient’s curiosity in order to get them to open and read the message.

On the other hand, we seek to lay the foundations for an interpersonal relationship, more likely to lead to conversion. Attracting and arousing attention is at the very heart of our considerations. PS. You have a lack of inspiration?

Don’t worry: we’ve prepared a list of items that will allow you to get at least 70% of openings. Just click here to access it; 🌳

5. Test your first contact emails

Nevertheless, and you know it as well as we do: marketing doesn’t take kindly to copycat techniques without any nuance. It’s crucial that you find your own subject lines – those that resonate with your audience enough to give you the best results. The best way to do this is to test a lot of items. Here’s an example of a campaign we ran:

  • Email 1 – A : Intro – Linkedin / B : question freelancing.
  • Email 2 – A : Re: question / B : follow-up.
  • Email 3 – A: link / B: info.
  • Email 4 – A: (no subject) / B: :'(.

The same campaign was duplicated 4 times. With 8 objects per email campaign, we managed to test no less than 32 different objects. This allowed us to quickly find the objects that worked best at each stage.

The next step will be to compile the best performing objects to produce a super-campaign made up of the best elements, which will guarantee you the highest opening rates. Be careful, however, not to make the mistake of looking only at the open rate (or click-through rate). It is crucial that the response rate is also taken into account.

Indeed, it can happen that an object generates a high open rate but negatively influences the response rates. So make sure you select objects that guarantee high rates in both cases. Now you know how to write a snappy email subject line! 🚀

Email subject lines FAQs

Many of you have asked us questions about email subject lines. So we’ve put together this short Faq, which aims to combine all the answers together. We hope these tips will help you launch your email campaigns. If you have more questions, contact our chat. 🤗

How do I come up with an idea for my email subject line?

Just click here to access a list of ideas. 🌳

Your email subject line needs to be original, if you don’t want to be invisible in the mass of emails your prospect receives. To do this, we recommend opening your inbox and going to look at the subject lines that seem catchy and might fit your target, write them all down, and then make your own versions. It’s not copying, just getting inspired. 😜

Be careful 🅰 email subject lines should absolutely not contain spam words. To discover the best practices of emailing and cold email, avoiding all spam filters, follow this guide.

Can we put an emoji in email subject lines?

Emojis help us convey emotions, they are catchy and trendy. 🤸 However, they make email objects impersonal and are often considered spam. We advise you to use only certain emojis and sparingly.

That is, only one per object, preferably smileys to convey a feeling: 😀😍🥵😉😱.

Avoid overly impersonal, business-focused emojis like: 💰🤑🚀🎯, in your email subject lines.

How do you write the subject of an email?

In the “add subject” section of your mailbox. No matter what your providers are: Outlook, gmail, yahoo, when you type a new mail, a space dedicated to the subject will appear. We advise you to add it first to avoid forgetting. 😱

If you are replying to a message that is already in a suite of “follow-ups” i.e. you are replying to an email, then the subject title has already been filled in beforehand, there is no point in trying to add one.

What subject for a spontaneous application?

For an unsolicited application, present yourself in the subject line in a playful way and arouse the interest of recruiters. Example:

I am an HR Assistant and you? I am interested in joining your team! Do you have a job opening? I have a key skill to offer you! Do you know what it is?

If you’re looking for jobs on LinkedIn, read this. 👀👀

What subject line for an intake email?

It’s your first contact, and you’re about to send a Cold email and you’re afraid it will be directly categorized in: “sales prospecting“? Use the methods suggested in the article :

The short and abstract subject lines have aroused your curiosity, which has prompted you to open the email in order to read its contents.

Are you more intrigued by an object that says “Hi, how are you?” or by one that says “-10%  UBEREAT”? Choose to intrigue rather than inform! (at least for the object) A newsletter will have a more elaborate subject, because (normally) your contacts have subscribed, so they know they will receive it.

How to send an email without a subject?

To send an email without a subject, simply leave the subject field blank.

However, we do not advise you to do so at all. It’s way better to send an email with the subject. The subject line is your only lever to motivate prospects to read more. Removing the subject line will do you a disservice, the email might even land in spam folder! 😨

How to change a mail subject on Outlook?

  • In Outlook, open the “Sent Items” folder.
  • Open the message with the subject you want to modify,
  • Then you just need to click on the “Other actions” button and then on “Modify the message”.
  • Correct your marketing subject.
  • Validate. 🚀

We hope we answered all your questions about email subject lines, if not, contact us on Waalaxy chat. 😁