Email is a great way to get reviews from people who want to help you succeed. There are a number of ways to do this.
The first and most obvious is to offer them something (such as a discount, a freebie, or a special promotion). See this website for a customer review email template to use for your business.
Another is to tell them a little bit about your business and why they should review it. But email is not just limited to that. It can be used to communicate about new products, special offers, and promotions.
You can even use it to thank people for their feedback.