Sending an email to each prospect before you call gives them an additional way to get in touch with you when they're ready. As you're leaving your voicemail, mention that you've sent them a quick email as well that has further details on who you are and the purpose of your call. As Florin Tatulea of Loopio explains:
After leaving four or five messages without receiving a response, you should stop calling – at least for now. Don't expect the courtesy of a call back from a hiring authority. Unless they have a need for someone like you, it is not likely that they will call you back. Don't take it personally. If you are looking for a job or soon may be, join Tony Beshara for a FREE webinar: The Top 10 Reasons You Might Have Trouble Finding a Job (and How To Combat Them).

Yes, you can make an email personalized, too. But voicemail is already much more personal than an email, and your level of customization should rise to meet that. Plus, if you’ve spoken with the contact in the past, there’s an even bigger opportunity to build on what you already know and cater the message to them.
That’s why it’s critical that each customer interaction with your business is consistent, positive, and represents the values and personality of your company. This includes your storefront, website, social media presence, emails, and every interaction you have with your customers, both online and in-person.