Throughout the long tenure of my voiceover career, I've had a lot of success finding clients through email marketing but it took a while to figure out the right words to put in the email. At first, I would try mass email programs, where every prospective client would get the same template. It was pretty formulaic and didn't have a personal touch. As a result, I wasn't getting a ton of positive results.
I started doing better research on the client to learn more about their business or product. Who they were targeting and what the marketing objectives were in their advertising. I began to personalize the emails with questions about their business. I made it more about them than me. That seems to stick! I started getting replies on how a voiceover could help their messaging. This method still works today!