Put Your Subject Lines to the Test

subject_line_testI’ve had the privilege of working with some pretty big clients on large-scale email campaigns that have taught me something valuable: humility. You see, just when I think I have a best practice for email subject lines, an A/B testing campaign comes along to debunk conventional wisdom and my best advice.

So now when clients ask me about subject line best practices, I tell them to assume nothing and test everything. The only way to establish a best practice baseline for your audience is to identify your controls and test until you beat them.

Not sure where to begin? Here are some of my ideas for subject line tests that could work for you.


You would think that personalization in your subject lines would consistently beat the open rates of non-personalized ones, but that’s just not the case. I have seen instances where subject line open rates drop with the addition of personalization, and other cases where the addition gives the rates a lift. Test two subject lines that are identical with the exception of personalization, and see how your audience reacts.


I have always believed that subject lines should be between 50 to 60 characters or risk being truncated in email inboxes, which could lower open rates. But yet again, I have seen instances where longer, truncated email subject lines have outperformed shorter ones with similar content. Take a longer subject line and test it against a shortened version to see which performs better for you.


If you think your offer-based subject line is a slam dunk for scoring high open rates, think again. If your offer doesn’t resonate, it might fall flat with your audience. Test offer-based subject lines against value-based ones. You might just discover that less is more when it comes to getting the open rates that you desire.


Don’t assume a subject line that works well with your customers is going to perform equally well with your prospects. Take your highest-performing subject lines and test them separately for customers versus prospects, and adjust your controls based on your findings. Be aware that too much familiarity with prospects can feel creepy, while lack of familiarity with customers can leave them feeling put off.


Try adding locality to your subject lines to see if you get a lift in open rates. Prospects may be more inclined to read an email that hits closer to home. Test different levels of locality: town, city or state.


Symbols aren’t just for B2C marketers anymore. I’m seeing an increased use of symbols in subject lines for B2B audiences. The fact is, symbols stand out on mobile- and client-based inboxes, and they can add enough interest and intrigue to make “scanners” stop and take notice. Test the use of symbols at the beginning, middle and end of your subject line, and test identical subject lines with and without symbols.

Want to learn more? Contact me for information about my email and subject line copywriting services.