Order Reminder for Magento 2
Magento Order Reminder extension helps increase sales by marketing to existing customers who have not ordered from your store in a while. It is almost always cheaper to market to your existing customers than to try and acquire new customers. Magento Order Reminder extension will e-mail customers who have not ordered in a while and encourage them to make a new purchase. You can setup multiple reminders / follow up intervals and you can even include an automatically generated coupon in the reminder to incentivize the purchase.
For example, you can email customers who have not ordered in the last 3 months. At month 4, if they still have not ordered, you can send them another follow up that includes a coupon to further encourage them to make a purchase.