Email subject lines: what influences their success.

Email subject lines matter. This is a fact we have known for some time. How well you manage to persuade your audience to open your emails depends on what you initially have to say in your subject lines.

There are so many things that can influence the success of your email subject lines; length, tone, and timing are all as important as the content and wording of the lines themselves.  Here are some factors that shape and colour a successful email subject line.




Personalisation is key to a good marketing campaign. In email marketing, this is no different.  Research shows that emails which show personalisation in their subject lines far outperform those that don’t. In fact, personalised email subject lines produce 50% higher open rates, 58% higher click-to-open rates, and double the unique click rates. To use personalisation effectively is no easy task. Many marketers merely use a name in the subject line, or imply that the email is going to be personal by use of a line with a direct tone or question, such as “so what’s in store for you?” This is all very basic and fails to touch upon any personal data gathered through previous interactions the customer will have had with your brand. Try mentioning previous purchases or basket abandonment of particular products to really make it clear that you know your customer and that they can expect an email that is packed with personalised content.




Due to the fact that over half of all emails are opened on mobile devices, it is now crucial that subject lines stick to a shorter length. Only 35 characters can be displayed on mobile, anything more and your subject line gets cut off, it’s meaning is lost and its impact subsequently reduced.

That’s not to say that email subject lines that are more than 35 characters and incompatible with mobile requirements, get ignored completely. Some consumers are in fact all the more curious by the sight of a cut-off subject line and are moved to open the email and discover exactly what the contents contain as it is initially not clear. A long subject line evokes complex content and this in spite of low attention spans can intrigue some consumers. Length varies massively across industries. Retail loves a short subject line, whilst other industries don’t. There seems to be no set formula, but you can’t go wrong with short snappy text that includes a specific offer.


Use triggers


You need to decide who you are aiming your email at and why. Is it a customer that has abandoned their basket, do you want them signed up to a newsletter, or do you want to re-engage their interest after a period of absence?  Offering money off incentives on next orders is a great way of re-engaging old customers. Promoting particular items that customers have abandoned from their carts in the past and birthday money off coupons detailed in subject lines are both great ways to get those emails opened. Again length is important here. Most longer subject lines which include incentives to complete a purchase can be read and understood without the consumer seeing the need to open the email, whereas short versions can invoke intrigue, prompting customers to open the email.




Surprisingly emojis can work well. In a recent study, emails with emojis in their subject lines had a slightly higher open rate of 26.67% versus 24.07% for those without. Positive responses occur if you use emojis relating to specific dates on the consumer calendar, such as Valentine’s day and Xmas.  Emojis add flair and character to subject lines, plus they allow you to encapsulate so much in terms of tone and theme, without using an excessive amount of text, saving you space. As always emojis allow you to connect with a younger audience.


What we’ve learned is that short, personalised, email subject lines that offer consumer incentives, result in the highest open rates. These subject lines do have to be written in a style reflective of the wider brand though.