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The Power of Subject Lines in Email MarketingOverviewSubject lines are such simple things – just a few words that are ofte...
Once the system for testing was in place we needed to decide what we were going to test. There’s a whole rangeof differenc...
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Email Marketing - Email Subject Line Case Study


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Email Marketing - Email Subject Line Case Study

  1. 1. The Power of Subject Lines in Email MarketingOverviewSubject lines are such simple things – just a few words that are often quickly pulled together, compared to thehours of planning and design and testing that goes into the average content of a marketing email.But much more focus should be given to them, as those few words are the quickest impact you can have on youropen rates. (Slow impact on open rates being from Deliverability and your From name / brand recognition). Overthe last year we’ve been working for several of our clients to improve the performance of their emails through splittesting subject lines.All the testing activity has been in the retail sector so performance can be tracked to sales. The primary objectivetherefore has been to increase sales, and therefore Return on Investment (or put simply - profit).The PlanThe overall aim was to prove that testing the subject line of an email on a small segment of the full databasebefore rolling it out would make a difference. We felt this was the quickest way for the tests to have an impact onperformance.In each test we: - Create the content of the email - Create 2 emails with that content: o One with subject line A o One with subject line B - Chose a segment of the client’s email database that has c20k similar customers in it - Split that data in half to create two test cells - At the same time on the same day send one of the emails to each of the test cells - 24 hours later look at the results and send the rest of the database the better performing subject lineWhen doing a test such as this there are some key things you need to take into account: 1. Make sure everything apart from the subject lines is the same on your test emails. So use the same HTML and text versions for each 2. Make sure you send to the 2 cells at the same time. This helps rule out any interference with the test results, and keeps things more valid. 3. Make sure you choose the right data to test with. The data should be of the same type – don’t test your oldest least reactive list against your best customers. You probably don’t want to use your best customers to test with – use your second or 3rd best segment, then you’ll maximise the return from the roll out because you’re able to roll out to your most responsive customers. 4. Make sure you have around 10k of deliverable data in each test cell. Generally this will give you statistically significant results – ie it ensures the results of the tests are valid and worth rolling out. Ideally you need to run statistical significance analysis on your own database to find the exact number you need in each cell, but as a rough guide 10k per cell should be ok.© indium online 101865 980
  2. 2. Once the system for testing was in place we needed to decide what we were going to test. There’s a whole rangeof differences you can test with subject lines so we quickly came up with rather a long list! They included: - subject line length - capitalisation - including the brand name - deadlines / sense of urgency - keywords – eg present vs gift - style – eg colloquial vs traditional phrases (Mothering Sunday vs Mother’s Day)ResultsThe headline result is that the testing drove a 30% uplift in sales.But there were a number of other interesting results we found too:  Which Metric to useIn deciding which is the best subject line for roll out you need to look at more than just the open rate. We sawsome big variations in open / click / conversion rate and AOV from the emails – quite a surprise as we wereanticipating the subject line only having a big impact on open rates. The stats we looked at included: - % of recipients that visited the website (click and open rate combined) - % of recipients that purchased (click, open, and conversion rate) - Sales per recipient (click, open, conversion rate, and Average Order Value)Quite often we’ve seen very different results from each of these for the same test!We settled on the Sales per Recipient metric as the primary objective of the emails we were sending was toincrease the Sales Value.  The impact of time on resultsThe best subject line after 24 hours wasn’t always the best subject line after a week. Again this was quite asurprise, but we decided to continue choosing the best after 24 hours as the roll outs needed to happen quickly(many emails have time sensitive offers).ConclusionIf you’ve got the volume it’s definitely worth testing subject lines. But be careful of which metric you use tomeasure success, and be aware of how the result may change over time.The tests also gave us some guidance on what we’ll be testing next: - Personalisation - Analysing the “final” results of each test to determine a subject line guidebook for each client© indium online 201865 980