We all know that inboxes get swamped over the holiday shopping season. Everyone – almost – is shopping, and every merchant wants to become the retailer of choice. The result is that open rates, even for brands that use personalization and personalized send times, can plummet during this crazy time of year. So how do you make your messages stand out? We dug into 89,932 holiday email messages we sent to discover which subject lines work the best. [Note: These tips are based on historical data from a smaller sample of messages spread across last year’s holiday season. Click here for a more in-depth look at subject lines from this past Thanksgiving and Black Friday.]

Here’s what we found:

It’s Not Actually ‘The Holidays’

Of course, retailers refer to the end of the year as “the holidays,” as do news outlets. But no one shops for the “the holidays.” They shop for Christmas, or Hanukkah, or Kwanzaa, or for the relative whose birthday just happens to fall on December 26. That may explain why subject lines with the word “Holiday” or “Holidays” don’t do particularly well. Subject lines with the word “Christmas,” on the other hand, had open rates 26% higher than “holiday” emails. Hanukkah-specific email was more rare, but enjoyed an open rate 40 % higher than generic “holiday” email.

Prices and Percentages Are, Surprisingly, Not Your Friend

Putting a price or a percentage in a subject line, such as “XX% off!” didn’t help open rates. In fact, they sunk them by 9%. An ambiguous “extra” percentage discount in the subject line didn’t do any better, with open rates 24% lower than average.

Aren’t discounts one of the best ways to get people to buy? Generally. But by placing the amount of the discount in the email, you’ve given people one less reason to open it. In a sense, there’s actually too much information in a subject line that says “10% off.” The shopper doesn’t have to open the email to discover the information that’s most important to them.

While an “extra” discount would seem to solve this problem, adding some much-needed ambiguity, it instead sounds slightly desperate and a bit fishy. Best to avoid.

Keywords DO Matter

There were a few subject line words that did seem more likely to entice customers to click. In order of awesomeness:

  • Discount
  • Bestselling
  • Deal
  • Top
  • Hanukkah
  • Joy
  • Christmas

Subject lines: bestselling

Those words that shoppers just didn’t seem to like?

  • Free
  • Midnight
  • Family
  • Bargains
  • Kids
  • Personal
  • Cheapest

This list shows, once again, why personalization is important. The word “kids” would obviously sink an email for a single person, but could do well among parents. “Family” has different meanings for different people, as well.

Don’t Obsess Over Length

There doesn’t seem to be a strong correlation between the number of words in a subject line and the email’s open rate. If you really want to nitpick, try for a subject line of 13 to 16 words, which have open rates about 15-35% better than the average. Performance drops off dramatically for 17-word subject lines, though, and pops back up a bit for 18-word subject lines. Maybe it’s just impossible to write a compelling 17-word subject line? Like we said, don’t obsess.

Forget About Word Length

There’s no evidence that shorter words in a subject line perform better than longer ones. Our analysis of subject lines shows that it’s way more important to write a subject line that seems engaging and relevant than it is to start counting characters. That’s missing the forest for the trees.

Learn to Love Emojis

Emails with special characters or emojis did a bit better than those without, and were 17% more likely to be opened.

So don’t just wish your customers a happy holiday. Go with a Merry Christmas, a Happy Hanukkah, or better yet, a bestselling discount in oh, about 15 words.

Subject lines: Emoji

Keep it Together, Folks

Yes, the holidays are exciting. But exclamation points and subject lines written in all caps are just flat-out annoying. Don’t do it. If you really can’t contain yourself, a subject line with one or two words in all caps presents no imminent danger to open rates. Everything in moderation.

The Bottom Line

With billions of emails about to be sent this holiday season, and billions of online commerce dollars at stake, marketers will be pulling out all of the stops to climb to the top of the inbox, and climb over your email! Ecommerce and retail professionals should, at minimum, earmark 10-20% of their holiday email subject lines to test the recommendations outlined above, and expand the test based on the results.