In order to create a successful email marketing campaign, you must constantly tweak your strategy. Looking at results, the hard numbers – opens, clicks, unsubscribes – gives us insight into who is opening the email and what they are clicking. Other aspects of email marketing are more ambiguous: the day and time of send, subscriber demographics and perhaps most importantly, the subject line. Some subscribers will never open or always open your email while others open emails based on subject line.

Our writers write strong subject lines but selecting subject lines is a game. They may all sound great but would one garner more opens than another? We tested this recently for a client with a straight A/B subject line test. We sent half the subscribers subject line A and half the subscribers subject line B. Another approach, which works well for large subscriber lists, is to send each subject line to a portion of subscribers, for example 5% get A and 5% get B. The number of opens determines a “winning” subject line, which is used as the subject line for the remaining 90% of subscribers.

In our particular test, subject line B had approximately 2% more opens than subject line A. We concluded it was good one subject line didn’t completely landslide the other because subscribers who want to read our emails will open it regardless of subject line. Both were strong subject lines but different, A cited a specific topic and B was general and prompted intrigue. The 2% difference was still significant and we analyzed the discrepancy further. We found the percent of clicks for subscribers who received subject line A was nearly 7.5% more than subscribers who received B. This could be because subscribers who opened A were interested in the specific topic, which prompted them to click links and learn more. On the other hand, subscribers who opened B may have been curious to find out what the topic was but found it irrelevant once they opened the email.

We can now tweak our next email campaign to get the results we want. In this particular case it’s a healthcare eNewsletter and we want to drive awareness and educate subscribers. Therefore, the direct specific subject line may show greater success for future campaigns.

Depending on the goals of the campaign and the behavior of subscribers, you need to implement different tactics. It’s all a game of hypothesizing subscriber behavior based on results. Subject line testing is a great way to read deeper into your subscribers’ habits and figure out how provide content strategically.