Designing effective email subject lines for action not open

Coinks Deals

Ever heard someone say the purpose of the subject line is to get the open? This is short sighted and the purpose and impact of the subject line goes much deeper, because it:

  • Leaves an impression for customers who don’t open
  • Frames the thoughts of the customer and changes what they do when reading

A perfect case in point is the impact of the subject line in a split test I undertook for Coinks Deals. The split test was part of a bigger strategy and optimisation around dormant customers.

I’m going to focus here on just one of the tests undertaken. A split test of these two subject lines:

  • Subject A: Are we still welcome in your inbox?
  • Subject B: Was it something we said?

The email creative was short and a mostly plain email with a few links and two main call to action buttons

Subject lines impact calls to action

Subject line B gave a 67% higher open rate. However, the impact of the subject line beyond the open was shown by the ratio of clicks on the above two buttons.

For subject line ‘A’ the ratio of clicks on the first button to second button was 6.5 whereas for subject line ‘B’ it was 2.8.

Put simply, customers with subject line ‘A’ were more inclined to click the first button. The test cell sample size was 12,000 and the difference in clicks was statistically significant.

The different subject line changed what the customer was thinking when they read the email and thus how they acted. “Are we still welcome in your inbox?” prompted the customer to consider this very question and whether their answer is yes or no. Whereas “Was it something we said?” does not prompt the direct question and the more conciliatory tone creates more interest in deals.

In the many tests I’ve run with many clients I frequently see that what happens in the email is skewed and changed by the subject line.

The subject line should be designed to get the right people to open not the most people. That means those most likely to take the action you want. Plus the subject line should frame their thoughts correctly.

The subject line is used by customers to self-qualify, if the subject line does not accurately qualify the right people, then customers who might have taken action do not open and conversely some open only to find it’s not the right message for them. In this case the risk is customers become less inclined to open again since they found they wasted their time previously.

Summarising two key lessons:

  • When testing subject lines don’t stop evaluation at the open rate. Look at the individual links clicked, the click heatmap and call to action copy for deeper insight of why a subject line caused a particular result.
  • Create subject lines with the call to action in mind. The power and impact of the subject line goes further than getting the read, it’s about getting the action and not just the read.

Incidentally this was just one test out of many over a series of four emails. The compounded gain for the desired marketing objective across the whole email sequence was an impressive 190%.