Easy breezy Beautiful Subject Lines

The art of subject lines

A great subject line is as important as a great email template. In fact, it is the first point of contact between your email and the recipient. Before reaping the rewards of predictive emails, you must first win the subject line battle. I’ve browsed the web to find tips on the topic and tried to combine all the findings into one simple formula, similar to Einstein’s famous mass-energy equivalence (E=mc2).

The component

In order to understand how to write great subjects line, we must first understand some human psychology basics, particularly the basis of influence. According to Robert Cialdini’s theory of influence, there are 6 key principles of influence:

  1. Reciprocity: People tend to return a favour, thus the pervasiveness of free samples in marketing.
  2. Commitment and Consistency: If people commit, orally or in writing, to an idea or goal, they are more likely to honor that commitment because of establishing that idea or goal as being congruent with their self-image.
  3. Social Proof: People will do things that they see other people are doing.
  4. Authority: People will tend to obey authority figures, even if they are asked to perform objectionable acts (not that you are going to be asking them to do anything objectionable).
  5. Liking: People are easily persuaded by other people that they like.
  6. Scarcity: Perceived scarcity will generate increased demand.

We will refer to those principles as Pn where n is the number associated with the specific principle (i.e: P2= Commitment and Consistency). In email marketing, each principle can be used in campaigns to not only get the recipient to open the email, but also to engage with it. You are most likely already using some of those principles without being aware of the psychological influence it has on the recipient.

Authentication (Au) is our second piece of the equation.Did you ever turned your head involuntarily to someone that uttered your name, only to find out that he was actually calling someone else? You have most likely experienced something similar because your name is the most important word in the universe for you. Your customers are the same so finding ways to originally authenticate them in the subject lines help grab their attention in the inbox.

Once you have your recipient’s attention, your subject line must have a trigger (T) that incentivizes them to open the email. Triggers usually lead people to take certain action because of the expected reward. For example, when a dog sees food (trigger), he salivates because he is anticipating the reward. In email marketing, the trigger is simply the main offer or topic of the email. For example, if you’re running a Buy 1 Get 1 Free campaign, recipients should know what to expect before opening the email.

The formula

The Formula

Authentication (Au) and Trigger (Tr) are like peanut butter and jam, they can both perform alone, but together they produce better results. Most importantly, they capture the reader’s attention within seconds. On the other end, the 6 principles (Pn) set the tone of the entire subject line. They affect how you use the authentication and trigger component to create an amazing subject line. That’s why the final formula is:

SB = Pn (Au + Tr)

where n is the number associated with P.


SB: Subject Line

Pn: Principle n (1,2,3,4,5,6)

Au: Authentication

Tr: Trigger

There you have it, a formula to create amazing subject line. Give it a try and please let us know if you’re getting better results or if there is an additional component to add to the formula.

If you like this article helpful, please share the love with your peers.

Receive weekly email marketing tips in your inbox


Written by Ned Nadima. Ned is a member of the growth team at rare.io. We also tweet about Ecommerce marketing at @rareio

Show your support

Clapping shows how much you appreciated Rare.io’s story.