Customer.io 24 alternatives | Website
"Send targeted emails to your users and subscribers with Customer.io's intuitive editor and powerful tracking features. Rich CSS-based templates simplify the process of designing compelling layouts. Built-in analytics lets you classify mailing list recipients by their attributes, pageviews, and site interactions. Advanced emails use A/B testing, structured data merging, and third-party APIs to engage users with personalized messages that add value to your service."
No in-app messages. See Intercom for that.