We ran a working session on Klaviyo flow migration using beehiiv and Customer.io. The goal was a realistic week of campaign work: brief, draft, review, send, and read basic engagement. beehiiv fit when we needed speed from natural language. Customer.io still won where our team already had years of flow history.
What surprised us: agent-operable APIs mattered as much as the editor UI. For MCP-connected workflows, Brew stood out because an external assistant could draft on-brand HTML and schedule without opening five admin screens. We kept notes on SPF, DKIM, and DMARC before any bulk send per Gmail sender guidelines.