6. Curiosity in the Subject Line

Curiosity is a psychological phenomenon that you can respond to in the subject line of your newsletter. Even scientific research has been done. If we do not know something, it gives us the feeling that we miss something and we are looking for information to eliminate that mistake.

But there is a subtle extra layer: it only works if there is a basic interest in the subject.

You do not get people curious with a question like "Do you know how many telephones are sold in 2015?".

For example, you can play with this:

9 out of 10 marketing managers make this crucial mistake

In the first example, everyone in marketing are addressed

The best hidden secret behind the logic of Google's search engine

(This example suggests the answer to the question of how Google really works, something that anyone with a website would like to see).