Back when I first started writing emails, honestly I didn’t think there was much to subject lines. How hard can they be to write, right?

Well it turns out it is a whole art form to craft subject lines (and headlines, slogans – basically anything where you are limited to a short sentence). What I love about this is the small things.

Let me introduce myself in a few words before we dive in. I am a senior copywriter at a content marketing agency and I've been working as a copywriter for 7 years now. During that time I wrote thousands of articles, dozens of email sequences, landing pages, ebooks, website copies and so on. I also give lectures about copywriting at trainings and workshops.

When I give advice about writing I always try to do it by showing examples, samples that either me or my colleagues personally wrote, or I came across, for example in my own inbox. This is what you can expect in the following series of articles about email copywriting.

A few months ago I was preparing to send out a free e-book to a list, which would strengthen engagement and direct recipients to our site.

It was not until the morning we were supposed to send out the newsletter when it struck me how should I phrase it. I did not write “gift” or “free” in there. This was my idea:

[Name of the boss] is away on a trip, so I quickly give you an e-book

And this brought 49% open rate and 20% CTR. Because it was unusual, personal and interesting. And when the idea came to me, I was in such a hurry to write it down that I left my half-drank coffee outside.

According to a study by Convince&Convert, 35% of people open emails solely because of the subject lines. (Of course the numbers may vary based on the sample and when the studies were conducted. HubSpot in 2012 found that this number may be as high as 47%.)

Image source:

C&C also says that out of those who report an email as SPAM, 69% do so because of the subject line.

It is truly an art of how you use words, what you say, how you play with emotions, target the right people with real solutions and so on.

In this article you will find some advice on how to write compelling and truly effective subject lines.

But the idea is not to give you only metrics and statistics. I want you to learn a mindset that can lead to moments like I had mentioned above.

Subject line basics – real quick

Let’s get over the obvious. A subject line is just like a headline of a landing page or an article. This is where you have to catch the attention of the reader. A more fitting example however are headlines of social media posts.

If someone visits an article or landing page, in some way they have already committed to that visit – they clicked on an advert, a post, a link in an e-mail.

Your email however is displayed in their inbox only because they have subscribed to the newsletter. They are not as committed, they are earlier in the funnel.

In order for the recipient to click on a link in your email you have to offer something different from all the others targeting that inbox – and that is a large competition.

In fact, the most common thing we don’t like about email is that we are getting so many.

A basic tactic is to use the 4U model and make your subject line:

  • urgent
  • useful
  • unique
  • ultra-specific

But what does it really mean?

Applying the 4U model in email subject lines

Urgency refers to scarcity. Create a sense that the recipient not only has to read this email, but has to do so right now. Because of a limited-time offer, recent and important news or because their competitors will get in front of them if they don't.

Being useful is self-explanatory: you have to give something to the recipient, something valuable. You are asking them to perform an action (open and read the email) so you have to offer something in return. Now this doesn’t have to be a discount or even a product, you are not selling your merchandise here, but the email itself.

Unique means you should try and be different from the other dozens of newsletters and junk mail an average user receives a day. We will get to this later on.

Ultra-specific can mean two things. One is personalization, which you should use very carefully. The other is much more important: you have to tell the recipient about the content of your mail.

These are the ground rules, but of course there is much more to writing an effective subject line. In the rest of this article we will cover some best practices which will help you craft yours.

How long should an email subject line be?

There is not much to say about ideal length. The best practice is to keep your subject line under 50 characters.

There are two reasons for keeping it short. One is that you want to summarize what you want to say for it to be easily readable in a single second. The recipient should be able to process it immediately, you will have plenty of opportunities to elaborate in the body.

The other reason is that subject lines longer than 50 characters won't be fully displayed on many platforms and email clients. Mobile users for example usually only see about 30-35 characters of the subject line, and by now most of us read email on our phones.

The Adestra Consumer Adoption & Usage Study tells us that on average 25,6% of users always read their email on mobile first and around twice as many do it “sometimes”. Mobile is especially strong in the 14-34 age group.

How to really use personalization?

Without doubt personalization is a very effective tool that can increase your open rates dramatically. Well, when you use it smartly anyway.

MarketingSherpa tells us that personalized subject lines can increase open rate by an average of almost 30%. Adestra says that the increase is 22.2%, although their data is from around 2013.

But this does not mean that you always have to personalize. Email personalization can be overused easily. If the recipients see their name in the subject line every time, they will get accustomed to it and it will be less effective.

Also, you should only use the name when you really have an offer that is personalized in some way due to remarketing or proper segmentation.

If you send me an email which offers something for me personally, and then in the body I see an offer which is in no way tailored to me or my segment, I will not forget it. I will assume that you were simply trying to trick me into opening the email, and since you were successful the first time, I will even feel frustrated.

What else can you do?

I’ll give you an example.

I have registered for a conference and of course ever since I’ve been getting emails with information and upsell offers. Now in the subject line they don’t use my name – they know it and many more about me, but it would be simply unnecessary.

Instead, every email begins like you can see it below:

With the phrase "T&C Attendee" I am not only addressed but also instantly know why I am getting this email.

To avoid overusing their name, other than segmented offers I recommend that you mainly use it when you send out trigger-based emails, like welcome emails, order statuses, thank you emails and so on.

Also, personalization in a subject line doesn’t mean using only the name. If you have more information, you can include the area or city the recipient lives in for example.

If you sell clothes and see that the weather will be cold the next week in a particular area where many of your subscribers live, you can send out an email to them offering warm clothes, warning them about it. This is a good, effective way to personalize your emails. This is called localization.

But other than names there are more words and phrases you should be careful with.

Words to use and avoid in email subject lines

There are countless lists available if you want to find out what can trigger spam filters – there are hundreds of words and phrases that can do that. The most common may be “free [anything]”, which is something you definitely don’t want to have in the subject line.

So instead of a list here we will tell you about the mindset you should follow, which will also help you to automatically avoid these.

As your goal is simply to get the recipient to click and open the mail, try not to sell anything here. The basic idea is not to sound like a door-to-door salesman. Instead focus on what is the value of your email for the audience and communicate that.

Let’s just have some look at the word “free” in detail so you get what I’m talking about.

First of all, using it is probably the best way to trigger a spam filter – just have a look at this small list from Yesware:

In some industries of course it still works, but in others, like retail, the results can be catastrophic:

Try to sound natural, not like a bad advertisement on TV. All marketing communication works best if it’s natural, if what you write sounds like something you could say in a conversation. This is why you should avoid the overwhelmingly enthusiastic phrases, like “perfect” and “wonderful” and so on.

You have a new article for me? Tell me what is it about. A new product? Tell me how it will solve a problem for me. Focus on what really matters to the audience. It is not the product, not the price, not how limited the offer is – it is the problem they have and want to solve. That will be the primary driver.

For example, if you want to sell me a lawnmower, don’t write this:

Don’t miss out on our BEST DEAL! Hurry up!

Yes, I usually receive emails like this.

Instead try something like:

I’ll give you more family-time. With a lawnmower.

Imply scarcity

By using certain words you can imply that your offer is very limited. Now this might be because of time or stock – the main idea is to use the “fear of missing out” (FOMO), which is an extremely well documented subject in modern psychology.

Time sensitivity for example can be implied using the words “urgent” or “breaking” with great results.

via OptinMonster

Now urgency itself is not enough, if you want to increase open rate and CTR, you must be also specific. I need to know why am I supposed to be worried about missing out. What exactly am I missing?

If you want to say there is a limited amount of a certain product, just say so. But if you do, be truthful – if you say there are only 20 products left, and I see on the product page there are hundreds or you don’t even have a stock counter, your message match will suffer.

Time-sensitivity can also be triggered another way. Let’s say you are preparing for a Christmas campaign. To be ahead of others, you will have to start it in November. But your message cannot be “get the best gifts” – by that time they will read and hear that everywhere.

But the gifts are not their main concern, it is time. They don’t want to spend the few days before Christmas with running around in shops Jingle All the Way style.

So emphasize that what they order now will be wrapped and delivered well before that and they can have a nice, calm and relaxing eve with the family, and drop the stress.

This is the way you can sell things that are out of season – implying that it is much better for them to act now, before everybody else.

Also, since I mentioned stress and fear, let’s talk about…

Positive versus negative messages

These are the two basic types of emotional massages. Both can be effective – emphasizing scarcity for example is meant to trigger FOMO, as described above.

But according to my personal experience positive emotions always prevail.

I don’t really want to make my audience nervous about anything – I want to motivate them, not because they need to eliminate a threat but because they want to make their lives better.

How can you do this? Well you can rephrase anything to be more positive. Like above, not saying how bad it would be for them by not taking the deal, but how good it will be for them when they do.

For a great example check out this campaign by PetFlow

When they put a discount on a certain product, they communicated it in a very creative way. Not by stating there is a "discount", because that is a cheap and dull way to do it, not to mention sounding exactly like SPAM.

They also didn’t say you should hurry to take it because you will "miss out".

No, they told their subscribers that there is some extra money they can spend. This is an overwhelmingly positive message which also instantly triggers curiosity.

Now the main message may only be true “from a certain point of view”, but that was fine by Obi-Wan and it was sure as well fine with the marketers of PetFlow because it delivered and wasn’t an outright lie.

You may want to chose your words very carefully also. Negative words tend to have negative impact. “Cancelled” for example.

Soure: MailChimp

If I cancel an order or reservation, why should I care about the confirmation about it so much that I open the email? The confirmation itself is right there in the subject line.

So instead try including something positive. Offer a “better” deal, “invite” them for another time, and so on.

Direct the attention

How do you get the recipient to instantly glance at a certain part of your subject line? You have to emphasize it some way.

Most of the time special characters are nothing but avoidable – they are known to trigger SPAM filters. Many use them to make the subject lines of their SPAM emails stand out without caring about how it would affect readability.

But this does not apply to brackets. Now if you put something in round brackets it comes off as some dismissible note or addition to the main message. Square brackets however are mostly used to clarify the message.

Have a look at these subject lines:

They do a great job at clarifying what the email is about – a new blogpost, a fresh case study, a limited offer and so on.

The first thing you glance at is those few words in the brackets, because you know it is the most important information, that will tell you if the rest is interesting or not. So if you want to be ultra-specific, this a good way to do so.

Should you use emojis and symbols in email subject lines?

Emojis are relatively new to subject lines, there are very few who use them and we don't really know yet how effective they are.

Certainly emojis, just like symbols, are great at grabbing attention, as they represent something unusual, a visual element where we are used to only text.

As of early 2017 there is no proof that spam filters are triggered by emojis, which is certainly good news. It may be surprising, but at this point all experts agree that they are not an instant trigger, so you can at least use them without the risk of ending up in the spam folder.

But how do they affect open rates?

Surprisingly well. According to studies by Experian, emails with emojis in the subject line get a 45% higher open rate than those not using them. 56% of brands who have tried using them report increasing open rates.

This leads to the conclusion that it is a useful tool and a really effective one, but you should always consider your target audience first. For example if you run a B2B newsletter and send out news, analysis and case studies to an audience that consists of professionals and industry experts, they may not be that receptive about the funny little images in the subject line.

It may be helpful to know that these are the most common emojis used in subject lines according to MailChimp:

What you should take away

Above I tried to give you an insight into how direct response copywriters work.

The most important thing may be the following.

Think about how can you be useful for your audience and communicate it while thinking about your relationship with them. Go further than a pure exchange of money and products. Think about what you are really giving them.

Comfort. Freedom. Less stress. Motivation.

These are the things they will feel when you solve their problem with your product and the things that all your messages should be based on.

So what is your best subject line? Share it in the comments!

Daniel Benyo

Daniel Benyo

Senior copywriter with 7+ years of experience