The email subject line is an important factor that greatly influences open rates and engagement. However, when it comes to putting a marketing email together, most of the planning and development goes into the content inside the email. The subject line is usually the last thing on a marketer’s radar and is generally put together haphazardly.
However, it is important to understand that the subject line is one of the primary factors that your recipients use to determine whether your email is worth their attention. So much so, that individual keywords can hold a big influence over whether your email gets opened or not.
Keywords subject line influence
Take the following example. In most circumstances the words “news” and “alerts” have, for the most part, similar meanings. But when it comes to an email subject line, the difference in using “alerts” over “news” is almost a 9.5% increase in open rates! Despite similar meanings, recipients attach positive or negative perceptions to certain keywords. These perceptions translate back to open rates.
Below is a small sample of words and the effect it has on an open rate (data supplied by Adestra):
| Keyword | Open rate vs average |
| Exclusive | 12.3% |
| Free | -3.0% |
| Gift | 12.4% |
| Latest | 8.3% |
| Only | -4.1% |
| Sale | 23.2% |
| Save | 3.4% |
| Download | 1.4% |
| Get | -8.6% |
| Register | -9.6% |
| Subscription | 5.0% |
Testing various keywords
Take note that every organisation and their list is different. Certain keywords are going to resonate better with your audience than others. In order to find out what works best for your communications, analytics should be run on past campaigns.
Highlight keywords to see their effect on recipient engagement and compare it to similar keywords or phrases. Also, try AB split testing subject lines and build an archive of words that perform the best. This will help you structure better subject lines in the future.
