Your opening line is always important. Whether you are performing a comedy sketch, making a political speech, picking up a date, or crafting a great email, you need a great opener. But how do you do this? What rules do you follow?

After compiling some research from companies like Litmus, Sendgrid, Return Path, Digital Marketer, and some quick data analysis of our BenchmarkONE marketing emails, we've found a few best practices that might help!

How long should my subject line be? According to Sendgrid, 3 word subject lines have the highest engagement while 7 word subjects are the most common. What’s always important to remember is that mobile devices (where about 50% of your contacts are reading their emails) typically only display 25-30 characters.

Are there any keywords that will help my cause? ReturnPath did a study of their own and found that these 3 types of subject line keywords performed best:

What else works? There are other types of subject lines that perform well and are worth considering:

Asking a question
​ex: Still doing it the old way?

Using humor
​ex: 3 Magic Rules for Keeping Gremlins out of Your Office Equipment

Offering a promotion
​ex: Save 20% on your next purchase
​
​Using Social Proof
​ex: Find Out Who Else is Using [Your Product]
​
​Saying something shocking or unusual (spark some curiosity)
​ex: WWF Wrestlers Share their Secret Tips for Entrepreneurial Success

Including something personal
​ex: Katie, check out our newest addition

Announcement and Invitation
​ex: You're Invited: Come See [Your Company's] New Display
​
​The "How To"
​ex: How to Get the Most Out of Your Day
​
​The Best (or Worst)
​ex: The Best Images of the Year

Pop-Culture Reference
​ex: Beyonce's Secret to Success

News
​ex: Forbes Announces the Technology of the Year

The one caveat here is that variety is the spice of life. Don’t do the same thing every time or you will wear out your list.
​

A BenchmarkONE Study

To confirm, deny, or illustrate these stats we decided to look at some of the great emails our marketing team has been crafting. We took a look at 15 different subject lines and their performance across 95,000 sends. Here's what we found.

Average Length: 4-5 words
​Highest performing (>30% open): 2-4 words

Keywords (or “power words” as we like to call them):

** Highest Performing: First name, Save

​Types of Subject Lines used:

Personalized (with the contact’s first name)
​ex. Hi, [Contact First Name]

Description (straightforward explanation of what is in the email)
​ex: The Marketer’s Guide to Hyper-Relevant Content

Download (offering a piece of content)
​ex: [eBook] Content Marketing Playbook

Bait (enticing idea that will be answered in the email)
​ex: We think you’ll like this winning marketing play

Promotion (special offer)
​ex: Save Some Bones

** Highest Performing: Personalized, Promotion

In conclusion, our best subject lines are short, sweet, and personal. We have also seen great success with our promotions – maybe that’s because we don’t offer them that often!

What works best for you? The rule is to test, test, test. Use a tool like CoSchedule to see what works best.