Why & How to Test Subject Lines on Your Next Email Campaign


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If you took a poll of B2B marketers (see below), my guess would be that only a small percentage test email subject lines with any regularity. The usual excuses given are 1) time and 2) risk – first, that testing subject lines adds one more step to the development of a campaign that’s already behind schedule, and secondly, that testing message to half the list runs the risk of lowering overall response.

Of course, the long-term benefits of testing subject lines far outweigh the risks. Yes, it’s one more step in the campaign process, but if you make testing a standard part of the routine, the extra time to develop test copy and set up the appropriate list splits is inconsequential. And yes, a single test message may not outperform the control, but the amount of risk depends on what you’re testing. Small, simple, isolated changes to your control message, especially as part of a systematic testing program deployed over time, render that risk fairly minimal.

The key benefit of a subject line test is not the lesson learned from one campaign. It’s the cumulative learning from systematic testing over time. If you’re testing correctly (see below), the difference in performance between control and test messages for any campaign will likely be small anyway. But over time, those small differences add up. Over the course of several campaigns, learning how your particular audience responds to different structure, topics, key terms – and then applying those lessons to each successive campaign, can increase email response rates substantially.

Furthermore, NOT testing subject lines is dangerous for one simple reason – you’ll never know what impact your chosen subject line had on the campaign. Let’s say, for example, that your campaign tanks (never happens, I know.) Was it because you chose the wrong message? If you used only one subject line, you’ll never know. But if you test subject lines, you’ll at least have a stronger sense of whether message, or offer, or audience, or list quality was at fault.

So you’re convinced, right? Here then are a few key tips for how to implement an effective subject line test:

1. Don’t try to do too much. Test only modest changes so that the test results mean something. If the two subject lines are completely different, no matter what the results, you’ll have no idea why one performed better than the other. Optimally, keep the structure consistent and vary just a word or a phrase. If you test consistently, you’ll be able to cover the bases and test most things over time.

2. Decide what it is you want to learn. Would it be most useful to know which of two key benefits matters most to your audience? Or which of two topics is more of a hot button issue? Or whether people respond better to a “white paper” vs. an “ebook”? Give testing a purpose rather than simply selecting two subject lines randomly to run head-to-head.

3. To minimize risk, follow a few basic principles. Keep in mind there are no hard-and-fast rules to subject line structure that work 100% of the time. In fact, if you tested 100 subject lines with every broadcast, I’ll guarantee that at least one of the top performers would break a few “best practices” along the way. However, for most B2B marketers, testing just two subject lines is the norm because list size won’t accommodate anything much more. With that in mind, it’s generally a good idea to:

– always include the offer (White Paper, Webinar, Ebook)
– include at least one key benefit (cut costs, save time, increase revenue)
– use action-oriented language (Learn, Register, Discover, Download, Act Now)
– keep the subject line under 40 characters if possible (roughly equivalent to the amount of text most recipients will see in their preview pane or on their mobile device before opening the email)

4. You don’t HAVE to test subject lines 50/50. Sure, it makes things easier on the reporting end, but if you have a control message or structure that performs consistently, and your list size is large enough that you can afford a smaller sample size, it might make more sense (and be less risky) to introduce your test message to only 25% of the list.

How often do you test subject lines? Take our poll below.

For more tips on B2B email marketing, download our free white paper: “Top 10 B2B Email Marketing Mistakes.”

Republished with author's permission from original post.

Howard Sewell
Howard has worked in marketing for 25+ years, and is president of Spear Marketing Group, a full-service B2B marketing agency. Howard is a frequent speaker and contributor to marketing publications on topics that include demand generation, digital marketing, ABM, and marketing technology.


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