7. The surprise effect in your subject line

Our brain likes surprises. A surprise gives us fun incentives. A subject line that gives a smile, an unexpected advantage or a striking thought chunk, distinguishes your email from the dozens of other emails in your newsletter reader's inbox.

For example:

What you can learn from Donald Trump about subtle communication?

Have fun pay more taxes

This may be one of the most difficult tactics.

If the content of your newsletter offers launching points, you definitely want to experiment with this.