Lesson 7 of 10
Subject line testing
A subject line has one job: make the right person curious enough to open, without tricking them about what is inside.
- Start with the reader, not the sentence.
- Read it out loud. If you would not say the sentence to a real person, rewrite it.
What you need to get right
Your copy has to do a small job fast. The reader is busy, distracted, and probably reading on a phone.
For subject line testing, start with the reader's situation. What do they already know? What do they need to believe before they click? What would make them stop reading?
Good email copy is not about sounding clever. It is about making the next step feel obvious and worth taking.
Do this before you send
- 01
Pick one thing to test: subject, CTA, offer angle, send time, or content format.
- 02
Write the decision you want the test to support.
- 03
Keep the audience and timing clean enough that the result is readable.
- 04
Run the test long enough to avoid reacting to noise.
- 05
Document what you will keep, change, or retest.
See it in a real email moment
Instead of 'June newsletter', try a subject line that gives the reader a reason to care: 'Your next campaign needs one job'. It is still clear, but it has a point.
Your quick todo list
- Write five subject lines: clear, curious, benefit-led, proof-led, and direct.
- Delete any subject line that promises something the email does not deliver.
- Pair the final subject line with preview text that adds a reason to open.
Check this before moving on
- The audience is specific.
- The email has one primary job.
- The CTA matches the reader's stage.
- The primary metric is chosen before launch.
- You know what decision the result will support.
Mistakes that quietly hurt results
- Using curiosity that turns into clickbait once the email opens.
- Repeating the same idea in the subject line and preview text.
- Testing tiny wording changes before the offer or audience is clear.
- Optimizing for opens when the downstream click or sale gets worse.