A marketing-automation and email-marketing platform best known for its visual workflow automation builder (site tracking, event tracking, lead scoring, conditional content, split automations). No forever-free tier — a 14-day free trial, then Starter from ~$15/mo for 1,000 contacts with unlimited emails, automation, landing pages, and forms; higher tiers add predictive sending, split actions, and custom objects. The deepest automation workflows of the four.