Email Subject Lines: How to Convert with the C.U.R.V.E. Method


Writing email subject lines can be either:

  1. An unforgiving onslaught of repetition that drains creativity and energy
  2. An exciting and rewarding challenge. An opportunity to improve marketing and communication skills

Our decades of experience writing and testing subject lines for companies of varied industries, business models and revenue bands helped us develop a unique method of creating subject lines called C.U.R.V.E. This new method improves effective writing and testing of email subject lines, while keeping the writer energized and learning.

Create Great Email Subject Lines with C.U.R.V.E.

There are five parts to the C.U.R.V.E. method:

  • Curiosity
  • Urgency
  • Relevancy
  • Value
  • Emotion

A good subject line should possess at least two of the five C.U.R.V.E. elements, and at least one of those two elements needs to be Relevancy or Value. An effective subject line convinces the recipient to open the email. Subject lines require flexibility, not necessarily best practices. The C.U.R.V.E. method doesn’t offer a suggested character length, capitalization rules, spam words to avoid, or punctuation guidelines. Why? Because email marketers must test subject lines; what works today may never work again.

Create Curiosity in Email Subject Lines

Curiosity, when used correctly, generates impressive email subject lines. However, curiosity should not be used in a click-bait manner. Build anticipation for the emails by teasing a preview of what’s to come inside. Sometimes marketers employ trickery as a curiosity element, but repeated trickery––especially with subscribers––is a terrible practice. “Piqued my curiosity” explains the sentiment well. An element of mystery arouses curiosity. If the subject line leaves nothing to the imagination, the email recipient won’t be curious and therefore, won’t open the email.

Adding curiosity in email subject lines does not always mean posing the message as a question. When using a curiosity question, make sure it’s an open ended question. A simple “yes” or “no” response can’t work. For example:

BAD: Are you Ready for Winter?

ME: Yes. (Delete)

GOOD: Want to spoil yourself like an Oscar winner?

ME: Yes. (Open)

Email Subject Lines Should Have Urgency

“Read this paragraph before it’s too late!” One of the oldest tricks in the marketing playbook, urgency can ultimately desensitize people. Telling people to hurry all the time can turn them off from your messaging. On the other hand, marketers can combine urgency with relevancy and value as a compelling tool in email subject lines. A retailer who constantly offers 25% off discounts can expect to see a rapid decline in interest and sales after the third or fourth time because people now expect a discount. The consumers know the sale will still be there next week and the week after, so why should they purchase anything right now? Give subscribers a reason to do business.

Some common and effective ways to build urgency in email subject lines include:

  • Setting a deadline
  • Applying the scarcity principle 
  • Using active voice

Reader Relevance is Key

Email subject lines need relevancy. Subscribers should be able to read a subject line and instantly recognize a need to open the email. Sometimes, relevancy requires adaptation. As certain aspects depend on outer circumstances, be sure to adapt the messaging to align with changes regarding consumers and customers.

For example: A mother with a newborn baby might find an email about diapers, baby food, or formula very relevant to her current situation in life. Ten years down the road, those subjects would no longer be relevant.

How does one harness relevancy? By connecting with the core values of one’s company and conveying those values to subscribers. What does the company stand for? Why should subscribers interact with the company? What message does the business promote? The values of products and services matter to the ideal subscriber. Abandoning those values undermines relevance. A great question to ask when crafting a subject line: “Why do our subscribers care about this?”

Communicate Value in Email Subject Lines

Relative worth, merit, or importance defines value. Products and services impact the leads, prospects, and customers––adding value by improving their lives. Think about white papers for example. People read them to gain knowledge, not for fun. The value isn’t in acquiring the knowledge alone. Rather, it’s in what we believe the knowledge will add to our lives (e.g., becoming better at our job, getting a raise, impressing co-workers, etc.). We wear cool shirts because we value how others think we look, not the shirt itself. To have a great relationship with subscribers, add value to their lives.

Emotions in Email Subject Lines

“SHOP NOW!” screams the subject line. Why all caps with an exclamation point at the end? Whose emotion is being conveyed? Is it the retailer’s or the subscriber’s emotion? Emotion is the most subjective element of C.U.R.V.E. It involves being authentic with the message conveyed in email subject lines.

Use emotions well. Let people know exciting news, but forget about using all caps or slapping an exclamation point onto the end. Simply be authentic. A new album from your favorite band elicits excitement. Paying $29.99 for the pre-order does not. “Happy Birthday!” conveys emotion. “Spend $20 and Save 15% on your Special Day!” does not. Emotion ties all of the other pieces of the subject line together. Find a genuine connection between the content and the audience to begin crafting a compelling email subject line.

Staying ahead of the C.U.R.V.E

Sometimes certain audiences simply need a different approach. The C.U.R.V.E method provides opportunities for the subject lines to impact the subscribers. Keep testing subject line elements to develop an email program that truly connects with the audience in a personal, authentic manner. 

Need some inspiration? Contact us. 


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Email Subject Lines: How to Convert with the C.U.R.V.E. Method

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