Customer retention is one of the hardest and most important things to get right in business. Tools and metrics abound for wooing and impressing new customers. Marketing analytics tend to focus on the point of conversion, and marketing budgets are often geared toward driving acquisition. New customers are exciting. They cause sales bells to ring. But your existing customers, the ones who have made the decision to stick by you, need some careful attention too. Here are a few email ideas to keep your existing customers engaged and happy with their experience throughout the customer lifecycle.