So you want to send promotional offers and coupons to your current customer in WooCommerce
Here are 3 methods
1- Use a plugin to get past customers email address. You can use this one. free. (https://wordpress.org/plugins/woo-order-export-lite/)and then upload it to a email marketing platform (sendinblue, mailjet, mailerlite etc..) prepare a mail over there and send.
2. You can buy this one from codecanyon https://codecanyon.net/item/woocommerce-custom-emails/13907681
4. You can use mailchimp and woocommerce for mailchimp plugin. problematic and no support but anyways.