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How to Write Perfect Email Subject Lines

If you’re starting out in email marketing or just want people to read your newsletters then this article is for you. Subject lines may seem easy, but there’s an art to getting them right. That’s why we’re here to show you how to write the perfect email subject lines.

You could write the best email in the world offering people everything they’ve ever dreamed of, without the right subject line, it won’t convert. Why? Because people won’t get that far.

Sloppy subject lines are the number one reason for low open rates in email marketing. If you’re struggling to get people to open your emails, then here are some great tips to supercharge your subjects.


Who said size doesn’t matter?

That’s right guys, people really do care how long your subject line is. Too long and you won’t be able to fit the whole thing in, too short and you won’t cause any excitement.

So what is the perfect length?

Well, it depends where you’re planning on putting it.

Devices can make a big difference to open rates. In 2018, 61% of email opens came from mobile.

The average inbox on a desktop will show up to 60 characters, whereas mobile inboxes show between 25-30.

If you don’t want your opening line to get lost, then try to keep these sizes in mind when writing your subjects. If there’s something that you think is important, but it’s making your subject too long, then you can always use the preview line to give additional information.

Important! - Information First

When writing your subject line, put the most important information at the beginning. You should do this for two reasons. Firstly, it lets people know immediately why they should open your email. Secondly, if your subject line gets cut off, then people still know what the email is about.

KISS - Keep it Simple Stupid

If you are using email for affiliate marketing purposes then you don’t need to write witty subject lines. You might be subscribed to mailers from big brands who write catchy headlines all the time. However, they are backed by strong house styles and brand image. Therefore, they need to ensure that every word written on behalf of the company speaks through their style. This isn’t necessary for affiliate marketing and isn’t recommended.

As an affiliate marketer, it’s your job to use email marketing to sell. You can use a bit of space in your emails to build trust, or even send the occasional non-sales email to your list. However, direct sales strategies work better for the quick sales you need for your campaigns.


Create Curiosity Through Questions

Questions are great for subject lines because they generate interest and the only way to get the answer is to open the email. Here are a few examples of question formats you can test out:

  • Is this the best [product] yet?
  • How much money are you wasting on [product]?
  • What is the best [product] available?
  • Is this the [product] of the future?
  • Have you heard of [product]?

Similarly, clickbait subjects which stimulate interest work well too. Just be sure to deliver on the promise by including the information people expect in the body of the email. Here are some examples:

  • 5 reasons to never use [product] again.
  • Why millions of people are using [product]
  • Don’t buy [product] before reading this.

You can get a little bit creative, but ultimately your aim is to generate interest quickly and sell. Therefore, make the product desirable, highlight it’s positive aspects and get people to the landing page. If you have any deals on the product, make the deal the core part of your email and subject line.


Don’t Spam Yourself onto Blacklists

If you’re new to email marketing then be really careful that you don’t fall into spam traps. Email providers really don’t like spammers and even the most honest campaigns can fall foul of the ban hammer. When that happens, your messages will fail to inbox and they’ll be lost in oblivion.

Spammy subject lines are fairly easy to avoid. There are certain words, characters and formats you shouldn’t use. Here are some of the main things to avoid if you don’t want to get blacklisted:

Special Characters

Special characters can be used, but use them sparingly and in their correct places. They key one to avoid where possible is the exclamation mark! It’s a key indicator that you are trying to get people’s attention and it will set the spam hunters on you.


There are a few formats which you should never use. ALL CAPS and number/letter c0mB1nati0n5 are two of the more infamous ones. Not only will spambots know when you use them, they aren’t particularly effective. ALL CAPS make people think you are shouting at them and number/letter combinations are ugly and hard to decipher, which will prevent your message from being understood.

Another format to avoid in your subject lines is a false sense of urgency. Telling people they need to Act Now or that the offer is only available for a Limited Time, will also see you enter the sin bin.

Don’t worry though, you can still create a sense of urgency by setting specific limits for your offers. For example: January Sale: 40% off - Ends this week.


Spambots get triggered by certain words in your email subjects and most of these should be fairly obvious. The top ones to avoid are:

  • Expletives e.g. S#1T, F$*K etc.
  • Free
  • Cash
  • Offer
  • Credit
  • Call Now
  • Click Here
  • Cheap

You might notice a trend if you look at all of the banned words and that’s because there are a couple of general rules applied here.

The first we already know, your subject line should not generate a false sense of urgency. The second is that your subject line is not your Call to Action, and anything that tries to make it a call to action will be seen as spam.

Basically, you want to get people to open your emails by generating enough interest to open them, without telling or tricking them into clicking.

Here are two examples of subject lines. One is spammy and one isn’t.

  • Click here to get your free copy of our latest Ebook! - ‘Spam on Rye’
  • New Ebook now available - ‘Spam on Rye’

To the untrained eye, both of these seem like fairly unassuming subject lines. However, the first one will probably have the spam police chasing you, while the second should slide straight into your list’s inboxes.

Admittedly, the second is less exciting, but at least if inboxes, there’s a chance people will see it and open it. But how can you jazz it up to boost your open rate?

The simplest way is to split-test and see what works best for your audience. Try to think a little bit beyond ‘We have a book, read it’. What type of book is it? Why should people read it? Are they fans of the author? Is it controversial?

Once you’ve done a bit of research, use that information to generate 3 to 5 subject lines for testing. Here are some examples:

  • New Ebook now available - ‘Spam on Rye’
  • Avoid spam traps with our latest Ebook.
  • Can’t get your emails to inbox? Our latest Ebook can help
  • Everything you need to know about emails all in one place
  • Whatever you do, don’t do this. How not to write subject lines.

Split-testing various formats like these will give you insights into what your subscribers are interested in and what makes them click.

Tell people who you are

Before you start sending emails to people on your list, make sure you have filled in details for the From Line. Otherwise the messages you send will show from an unknown sender, which makes people instantly think that the email is spam.

Make your name easily remembered and recognisable. One way to make sure that people know who you are and open your emails is to create welcome emails. Welcome emails should be sent when people subscribe to your list. If your name bears a relationship to where they signed up or what they signed up for, then there will be no confusion.

If you don’t send anything until a few days after they opted in, then they might have forgotten all about you. This can lead to spam complaints and subsequently blacklisting, even if you haven’t done anything wrong.

The Bottom Line

When it comes to writing email subject lines, practice makes perfect. Avoid the most obvious mistakes and then get experimenting. Only you can know what your audience really wants and you can only know that if you keep testing. Don’t be afraid to try new things. You will have successes and failures, the key is to recognise these and learn from them.

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