Does the ideal email subject line exist?

Did you think investing some extra time to find a good subject line was not that important? Think again!
(And please spare a minute to read these tips of our Marketing Automation team so you can do better on your next mailing.)

So what IS a good subject line anyway?

To answer this question we need to take a look at the importance of a good subject line.

Well, one thing is certain: in this busy enamel times, as we are constantly battling for the attention of our recipients in their inboxes, good subject lines really are essential.

Good subject lines are attractive, not too short but certainly not too long. They are inviting recipients to open the mail, to discover the content and to continue their reading.

To check how well your subject lines are working, take a look at the unique open rate or view rate. This is the ratio between the number of unique opened mails divided by the number of unique delivered mails. The more recipients open your e-mail, the more likely it becomes that they will actually read the content of your email or at least will scan the text. Please note that this metric is distorted by the fact that some recipients will open your mail without downloading the images, which means that they are not included in this metric, as the correct loading of the tracking pixel in your e-mail is the signal to mark an email as opened. (Especially in a B2B context, the share of this group may rise considerably)

When evaluating email campaigns use all available metrics. Personally, I find the Click To Open rate (or CTO) is very important because it gives us an idea about how interesting the person who opened the mail thought the content was.

But back to our subject lines now.
Let's take a look at all the aspects that can play a role:

The perfect lenght

The following question regularly pops up: ‘How long should my subject line be’?
Until a few years ago, my answer would have been: between 50 and 70 characters, but given the increasing share of 'mobile opens' I now tend to advise a maximum of 40 to 50 characters.

verdeling lengte tov uitgestuurd

Above: Distribution of the lenght of subject lines versus the number of emails sent


With those 40 to 50 characters you are also safe in terms of email client compatibility: not every client shows the same number of characters.


Choosing your words

All those who regularly send out email campaigns will certainly have noticed the following: the same email action at times scores much better or worse, and this while the mail’s content was completely similar or even identical, and while the time of delivery was the same. Why is this? Well, the content and meaning of your subject line play an important role, regardless of the actions of competitors, of the attractiveness of your offer or any external factors.

It all comes down to choosing words that work well and that are responsive to the psychology and the context of the recipient. Words such as ‘now’, ‘last days’, ‘only today’, ‘exclusive’, ‘just’ ... create urgency, while words like ‘saving’, ’benefit’, ’promotion’ or ‘2 + 1’... should make it clear that the offer is very interesting indeed. However, be very careful with the words ‘gratis’ or ‘free’: they can cause your message to end up in the spam folder of your recipients. Sending out emails in multiple languages? Then be sure to test these aspects for each language and do not just assume that your findings are always true for every language.

And what about personalization?

For a long time, the use of a name in the subject line was mentioned as an important must-do to improve response. However, research has shown that this is certainly not / is not always the case. On the contrary!

The use of location in the subject line, certainly in combination with another element like a question, always works really well. Major media players often successfully use this type of subject line, especially when it comes to emails where segmentation based on geolocation is obvious, such as regional newsletters: eg. ‘Wondering how well politicians  doing in Ghent?’ or ‘Has the number of burglaries decreased in Aalst?’

Even the use of "je" in Dutch, or ‘tu’ in French, versus the more formal ‘u’ and ‘vous’ can make a difference in the acceptance of your message.

For a long time, it was believed that the use of uppercase (capitals) was to be avoided at all times, especially because this increased the risk of being mistaken for spam. However, today we dare to question this negative impact. Moreover, sometimes this works very well. (Here the very opposite is happening from the negative trend in the results for personalization by name, mentioned above.)

Conclusion: things that worked well before, therefore, not necessarily still work today and vice versa. So always keep this in mind when working in email marketing. This last example will perfectly illustrate this: to end this blogpost, let’s talk about the use of emoji or special characters and punctuation marks in your subject line.


Example of a subject line with Emoji's in (web client).

In the beginning, the use of emoji made sure your message stood out in the inbox of the recipients. But now that more and more players start using them, it is possible that this positive effect is fading quickly. Please also note that not all email clients provide the same support for these emoji.

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