Five Keys to Executing a Meaningful Email Marketing Test

The number one rule of email marketing is to ALWAYS be testing some aspect of your email. Successful email marketers have developed some well-defined best practices for how to run a test, whether you’re varying subject lines, images, colors, or calls to action. Because it’s the most common, let’s use a subject line test as our example:

  1. Only test one thing. This means you are only testing your subject lines, and the rest of the email is identical. You can certainly test more than one subject line against one another (we don’t recommend more than 3–4 against each other, and that depends on the size of your email list), but the only difference between each email should be the subject line. That way you can clearly declare a winner knowing that no other aspect of your campaign influenced it.
  2. Always test against your control (the winner of your last test).
  3. Depending on the strength of the test, and using your best judgment, either use a 50/50 split test or an Nth% test.
    1. 50/50 Split Test (also called an A/B Split): 50% of the email addresses receive the control subject line, and 50% receive your test. You can imagine that this could be performed with 3 or 4 subject lines, by splitting the list randomly in thirds or fourths, respectively.
    2. Nth% Test: The majority of your list (say, 75%) receives your control subject line, while a smaller percentage receives the test. You could imagine performing an Nth% test first, and if the test subject line is the winner, you may want to run a 50/50 Split Test with your next email (using the same control subject line and same test subject line).
  4. Establish which metrics you’ll use to declare a winner prior to sending the email. For a subject line test, the typical metric will be the open rate. However, looking at the click through rate of those who opened is another great thing to take note of.
  5. Email marketing has a tail of when people open it, so give your test about 24 hours before you analyze your key metrics and declare a winner.

Remember, you should always be testing some aspect of your email marketing, but don’t be scared to go with what works. If you’ve got a winner, there are plenty of other things to test, so move on to the next until it’s time to circle back to the beginning.

Stay tuned for our next email marketing blog post, where we’ll tell you the 9 tests you MUST be running.