Testing email subject lines: we all know that we need to do it often, but with so many other things on our email marketing plates, from usability to testing more mundane things like rendering, many email marketers give testing subject lines less priority than they would like. Yet, with some careful planning, subject line testing can get done more efficiently and effectively than you’d think. The key is to work from your strategy, and your gut. And to test less often, and test fewer subject lines, than you think.

Why test fewer subject lines? Because you have already tested scores of them, if unconsciously, through your daily email messaging. If you’ve been marketing to your list for a while, you understand that list and have a gut feel for it that often can’t be put into words, but is your strongest asset when determining which subject lines to test. You’ve been watching open rates and clickthrough rates, and have a sense of what type of subject lines resonate with your audience, based on measures of their past behavior. You even have a sense of what resonates with different segments. You really do. You know if your core buyers like humor. You know if new customers resist too many on-boarding messages by unsubscribing. You know if time-sensitive offers for your costlier lines lead to high clickthroughs, but also high rates of shopping cart abandonment. Verify these gut instincts by carefully reviewing past email metrics, and you may find you don’t have to test a specific line after all. Because there is no such thing as a unique subject line. The words may be different, but the concepts behind the line, and, more importantly, the strategy, are the same for each basic category of subject line, such as time-sensitive offers, benefits-laden offers, price-based offers, and humorous or intriguing lines. If you can identify a basic strategy that has worked based on historical data, then you have identified an effective type of subject line. It’s important to look at the overall strategy that a subject line reflects, rather than focusing narrowly on the exact wording. With a strategic focus, you cannot go wrong. You can also pour fewer resources into testing, and more into developing stronger creative, and expanding your email marketing into specific campaigns for social and mobile.

So if you can avert a lot of testing with a strategic analysis of your existing metrics, when should you test? Here are some good rules of thumb on when testing is essential: 

  1. When even your best subject lines are underperforming: whether the underperformance is new phenomenon, or a longstanding problem, it’s time test some new creative. Of course, the problem may not be your subject lines; it could be the list, the time of year, or the market, but whenever an email program underperforms, it’s time to work reconsider every aspect of performance.
  2. When targeting a new customer segment: whether you’re entering a new market, or just re-evaluated your segmentation and created new segments within your old lists, it’s time to test which subject lines resonate the most with this new target segment.
  3. When you have the creative urge to try out new types of subject lines. Your list is doing well, but you understand the need to keep email creative fresh to keep your customers engaged. You’d like to try a new strategy. That’s great—now test it against all of your existing strategies to make sure it works.

Once you do identify a need for testing, make sure to test the strategy, not just a specific line. And remember, although you’re being more selective on what you test, you’re also being very thorough once you do decide to test. If you’ve decided to go time-sensitive, create a series of time-sensitive subject lines and test them against all segments and against several other variables, such as time of day, and day of the week. Test with different types of creative, if your budget allows. This way, you’ll know your new strategy is effective, securing vital buy-in for what could be a whole new creative direction for your email marketing. With a streamlined testing approach, you can maximize your return on email and add more subject lines to your messaging arsenal.

Author: Christina Inge