Call to action (CTA)
A button, link, or phrase that drives readers to act. Examples: "Buy now" or "Read more."
In email newsletters, CTAs are typically one of two things: click or reply.
Unless your newsletter contains variety content (e.g., industry news) it's generally best to focus on one call to action. In addition, it's advisable to make sure your call to action displays above the fold on mobile to maximize clicks.