Are you beating the spam filter?

The importance of email subject lines

Subject lines are probably the most important part of an email. This is what subscribers see in their inbox. If it doesn’t tempt them to click, your marketing efforts are ultimately a waste of time, money and resources. 

It doesn’t really matter how good the content of an email is and how well-crafted a campaign is. If the recipients never open them they are worthless.

What exactly is a subject line?

A subject line is the single line of text people see when they receive your email. This one line of text can often determine whether an email is opened or sent straight to the trash – that’s if it even makes it past your subscriber’s spam filter – so it is important to make sure it’s optimised for your audience.

Most email inboxes also display a preheader. This is the text that follows the subject line and gives a preview of the content of the email. These are a great way to further tempt a subscriber to open the email, by giving a glimpse of the value contained within it. The aim is to complement your subject line not to just repeat it. 

Why is your email subject line so important?

The subject line and preheader are the only thing that recipients can see when your email arrives in their inbox. Think about the hundreds – or maybe even thousands – of emails you receive yourself every week. Do you open and read them all? Maybe you delete some without reading or mark some of them as spam? Your behaviour in this respect is probably fairly similar to many other people.

With the overwhelming amount of digital correspondence we are subject to, it is understandable that we choose to filter out messages that don’t interest us.

Invesp found that 47% of people decide whether to open an email based on the subject line alone. It stands to reason then, that if your subject line isn’t clear and catchy, your email is at risk of being ignored. 

Surely everyone can string together a few words and whip up a decent subject line though, right?

Wrong. Writing short copy takes more than just good writing skills. You need the knack of condensing a larger message into a few words, whilst also appealing to your target customer.

Spending a little extra time on your email subject lines will pay dividends. More potential customers will open your emails, emails won’t be delivered to spam, and your message will be delivered to the right people.

What makes an effective subject line?

As with many things in marketing, there is unfortunately no one right answer. It is perhaps not as much of a mystery as the infamous Instagram algorithm but there is certainly no ‘one size fits all’ when it comes to subject lines. There are however some guidelines, based heavily on research, that should help in constructing an effective one.

  1. Keep it short

The general consensus is the shorter the better, particularly as many people now view their emails on mobile devices with smaller screens. Invesp found that subject lines with between 6 and 10 words had the highest open rate (21%). Increase that to 21 words or more and the open rate dropped to 9%.

  1. Avoid spammy language

We’ve all received a spam email at some point and are familiar with the all caps subject lines and multiple exclamation marks they often involve. Avoid the other classic spam features such as overtly ‘salesy’ language – like “Buy now” and “Free” – and this should help you to avoid the junk folder.

Instead of making it about sales, make it about value; what can you offer or share with the recipient.

  1. Use open-ended questions

Questions as part of your subject line are great for catching your readers’ attention. As humans we are naturally curious; seeing an unanswered question piques your interest and makes you want to find the answer – which you can do by opening the email – therefore giving a higher open rate.

  1. Urgency

Creating a sense of urgency prompts people to take action. By adding information to your subject line about the start and end dates of a promotion or sale, for example, interested customers are likely to click to see what they can get within the window. You could also use a series of emails as a countdown to the start or end of an opportunity.

  1. Use action-oriented verbs

Some people respond well to direct instructions so incorporating action-oriented verbs – similar to a call to action – into your subject line can be successful, particularly when selling tickets to an event or trying to gain subscribers. For example, when selling gig tickets, using something like “Dance the night away with us in London” is more enticing than “London Gig next month” as it helps the reader picture themselves actually dancing at the gig.

  1. Make announcements

If you have something new to share with your subscribers or customers, get it in your email subject line. The recipients will feel as if they are amongst the first to know about the news or offer and it boosts the sense of personalisation.

  1. Consider personalisation

Using personalisation tokens – like name or location – in a subject line makes the reader feel valued and creates a rapport with the sender. Research has shown that non-personalised subject lines had open rates of 14.1% compared to 21.2% for email personalised with names and 22% for emails with another type of personalisation. If you can’t (or prefer not to) use personalisation tokens, using ‘you’ and ‘your’ within the subject line feels personal as it sounds like you are addressing your reader directly.

  1. Be unique, unexpected or funny

With the large amount of emails we receive every day, standing out is difficult. If you can incorporate humour, maybe by using puns or wordplay, or include something unexpected like an eyebrow raising statistic or little known fact about your industry, you are more likely to catch the attention of your recipient. The novelty factor will also increase the likelihood that your email will be remembered later on.

  1. Use emojis

Emojis are a fantastic way of supplementing your message, conveying emotion when space is at a premium and making your emails stand out in an inbox; amongst a wall of text, a cheeky little ghost, burger or dancing girl will jump right out. According to Experian, 56% of brands using emojis in subject lines had higher open rates. It is important to remember to use them sparingly with most research finding that you should use no more than 1 at a time


By using some of these tips, we are confident you can come up with some creative and attention-grabbing subject lines of your own. However, it is important to look deeper. Put yourself in your subscribers’ shoes and think about your own inbox and which emails you open, delete or unsubscribe from. Even better, conduct some A/B testing using email marketing solutions to really help narrow down your target audience and their behaviours. If you need some help with this, get in touch now with one of the experts at TDS.

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