Klaviyo is the e-commerce email and SMS marketing platform that has become the default for Shopify and DTC brands. Its AI features include predictive analytics (expected date of next purchase, lifetime value prediction, churn risk), smart send timing optimization, and AI-generated subject line testing. The segmentation engine lets you build highly specific audiences — 'customers who bought X but not Y, who haven't opened an email in 60 days, who are predicted to make a purchase in the next 30 days' — and automate personalized flows for each. The depth of behavioral data from e-commerce integration makes this segmentation genuinely predictive rather than just demographic. For e-commerce brands that take email marketing seriously as a revenue channel, Klaviyo's combination of data depth, AI predictive features, and Shopify native integration is the clear market leader.