What are excellent calls to action to help email marketing convert to sales?
Some of the best calls to action feature a sense of urgency and/or exclusivity. They should be clear and relatively short. You’re asking specifically about sales, but CTAs can be used for any action you want your email recipient to take.
For sales, I would learn from what converts best on your ecommerce site. If “Add to cart” performs better than “Buy now,” I would extend that to your emails. Your sales-focused CTA can also point to a particular element of the sale you want to make. For example, “Use your discount” or “Save $X now” not only provide a sense of urgency, but also have sense of exclusivity to the person receiving the email.