Q: Does capitalizing one IMPORTANT word in your subject line increase email open rates?

Sometimes with the Stash we try to dig deep and uncover hidden ideas. But other times we just want answers to simple, common questions. For the next few weeks we’ll be doing just that around the theme of email subject lines. Today the point of analysis is whether capitalizing one important word in your subject line will increase the open rate of that campaign. Let’s see what we find.

The Goods
To find our answer we looked at 50 mountain resorts that had used multiple subject lines both with and without an all-caps word. The most common word was free (i.e., “Buy 3 Nights, Get One FREE”) with sale, powder, alert, and sale showing up regularly as well. Here’s how the data points look:

In this case, adding an all-caps word had absolutely no overall effect on the open rates of the campaigns in our sample. In fact, we had to go to the 3rd decimal place to see any difference between the percentages. It’s safe to say that some things significantly impact how many people open an email, but this isn’t one of them.

What This Means
It’s not to say you should or shouldn’t use an all-caps word, but it’s probably not worth wasting time debating if the issue at hand is performance. Though it is good to remember that, like exclamation points, all caps words can trigger some spam filters.

Instead, use it when it fits and don’t when it doesn’t. Concern yourself with other elements of your subject lines if it’s important to your goals, but this probably isn’t one worth thinking too hard about.