New studies have recently come out to provide a fresh look at how consumers view the marketing emails that hit their inboxes each day. Two years ago, the average consumer could expect to receive more than 400 commercial emails in a month, creating a cluttered communications experience for them.

A study from Return Path analyzed 9 million subject lines that were sent to 2 million consumer email accounts during the first two months of 2015. While previous research found that the length of the subject line was inversely related to the open rate, this study did not. Of course this doesn’t necessarily mean that it’s not something to keep an eye on when sending marketing messages.

While shorter subject lines may have inspired the highest open rates in the past, this recent study found that the highest open rate went to subject lines ranging from 61 to 70 characters. Although this open rate was double what subject lines of over 100 characters received, only a small percentage of subject lines used this many characters. The most common length of subject lines in this study was between 41 and 50 characters.

The reason to continue paying attention to subject line rates even though shorter isn’t always more frequently opened is that not all devices show the same number of characters. While a desktop mail client will usually show about 60 characters of each subject line, mobile email only shows about half that. This makes it critical that marketers with a high base of mobile customers keep their subject lines concise if they want them to be fully seen.

When it comes to keywords, the study showed that the following perform above average:

  • Still time +15.54%
  • Register +6.7%
  • Fastest +5.3%
  • Steps +1.23%.

While “how to” subject lines showed average performance, the following keywords performed below average:

  • Secret of -8.69%
  • 2for1 -6.62%
  • Running out -3.3%
  • Cheapest -2.94%
  • Announcing -1.45%
  • Buy -1.25%.

A Phasee study looked at 700 million emails in the US and UK covering the e-commerce and retail sectors. They discovered that personalizing the subject lines of marketing messages inspired a higher open rate, with “just for you” doing particularly well – even better than using the subscriber’s first name. Including brand names in the subject line can be useful for increasing open rates. Also, if you plan to ask a question in the subject line, closed-ended questions fare far better than open-ended questions.

The study scored several retail and e-commerce keywords and found that the top performers included:

  • Celebrate
  • Delivery
  • Love
  • New lines added
  • New products
  • Plus free delivery.

This shows a clear opportunity for marketers to increase their open rates when they incorporate the keywords that inspire consumers to most frequently read their messages.


Marketing Charts. Email Subject Lines: The Latest Data. May 5, 2015.