These are top and recommended Follow Up Email Extensions for Magento 2
1) Follow Up Email by Landofcoder

Using Magento 2 Follow Up Emails will support and ensure the satisfaction of customers. The better follow-ups are, the more chance to interact with customers and increase the sale.

Link: https://www.mageplaza.com/review/magento-2-follow-up-email-landofcoder.html

2) Follow Up Email by Mageplaza

Magento 2 Follow up email is one of the most powerful tools that increase conversion rate and drive more sales into your store.
Link: https://www.mageplaza.com/magento-2-abandoned-cart-email/
3) Follow Up Email by Aheadworks

Follow Up Email for Magento 2 will be an effective application that makes the strong connection with customers. It will automatically send the emails to followers.
Link: https://ecommerce.aheadworks.com/magento-2-extensions/follow-up-email
4) Follow Up Email by Goivvy

Follow Up Emails made from Abandoned Cart Email Magento 2 extension is so helpful for your stores to approach more and remain customers.
Link: https://www.goivvy.com/abandoned-cart-email-magento2.html

Also check Follow Up Email by Mirasvit: https://mirasvit.com/magento-2-extensions/follow-up-email.html
They provide very powerful email designer and analytics for emails.

Mageants also provide magento 2 follow up email extension view here https://www.mageants.com/follow-up-email-for-magento-2.html