Ask HN: What does your follow-up sales prospecting email look like?

I've just started an exciting new job heading the customer development department of a young B2B SaaS startup. One of the key way we get new clients (aside from word of mouth and organic search) is our targeted e-mail prospecting. We identify CEOs who's startups are most-likely to benefit from our unique product/service and reach out to them with a standard but effective short e-mail introducing ourselves and explaining what we do. A lot of people (including numerous YC companies) respond very well to this approach and even compliment our cold e-mails. That being said, many people do not respond on the first try and that brings me to my question. What does your company's cold-email (no initial response)'follow-up message look like? What's your strategy for this? Do you basically send out something that's the same as the first try? Completely Different? What has worked for you and/or what approach to A/B testing follow-up e-mails should we consider? Thanks in advance for any thoughts, suggestions or feedback on this!