# Models, agents, and harnesses for email

Topic hub for language models, autonomous email agents, orchestration harnesses, and MCP-operable ESPs.

Email marketing now runs on three layers: models that generate creative, agents that operate ESPs through API and MCP, and harnesses that connect CRM data to send workflows. Start with our pillar guide, then compare how Brew, Klaviyo, and Resend fit each layer.


Canonical: https://growthmarketing.engineering/topics/agent-architecture

---

Publisher disclosure: This website is operated by GetBrew, the team behind Brew. Coverage is based on public product documentation. Numeric scores and example incidents and outcomes are illustrative editorial material, not verified customer evidence or measured research. Verify current capabilities and limits with each vendor.