Emails must be short and hyper-personalized with advantages, not features.
Take advantage of free resources that connect you with folks who have been in the sales game longer than you for external perspective and community.
Books to read: The Name of the Wind by Patrick Rothfuss, The Transparent Sales Leader by Todd Caponi, The Challenger Customer by Brent Adamson
KPIs for a renewal-based business are based on clients who are most likely to renew, so look at which industries and revenue bands are most likely to continue, and if they are renewing flat or with an increase.