Mails.ai vs Warmbly

Mails.ai provides email infrastructure and an API for AI agents to send, receive and parse transactional or conversational email. It is available on the web and through an API, with REST, webhooks, an MCP server, and TypeScript and Python SDKs. Inbound replies arrive as structured payloads containing sender, subject, body, headers and attachments, as well as an injection score and sender reputation. All plans scan inbound messages for prompt injection; optional classification can extract intent, entities and urgency for $0.003 per inbound. Listed integrations include Claude Code, Cursor, Cline, Continue, Windsurf, OpenAI Agents SDK, Anthropic SDK, LangGraph, Mastra, Vercel AI SDK and Pydantic AI. The maker describes the product as early, live and self-serve, and says the API refuses cold outreach. Free costs nothing for 3,000 events and one agent. Pro is $20 a month; Scale is $99 a month. Sends stop at a plan's monthly cap; excess inbound replies are stored but not scanned or sent to the webhook. The maker says it lacks SOC 2 today and does not include HIPAA in Phase 1 scope.

Warmbly is an open-source cold outreach platform that brings email warmup, campaign sending, a unified inbox, analytics, and CRM together. Campaign sequences can branch based on opens, clicks, or replies, include A/B variants, and send follow-ups in the same conversation thread. Sending can be restricted to weekday working hours in a selected timezone. The inbox classifies replies, bounces, out-of-office messages, and clicks across connected mailboxes. Warmbly is available on the web and through an API, or can be self-hosted under Apache 2.0. When a self-hosted installation connects to Warmbly Cloud for warmup, campaigns, contacts, and inbox data remain on the self-hosted server. Integrations include HubSpot, Salesforce, Pipedrive, Close, Zapier, Make, n8n, Slack, Discord, Calendly, and Cal.com; Google Sheets lead sync is available on demand. The free warmup pool supports up to 10 mailboxes. Paid campaign plans include Starter at $23 a month billed annually, with 150 emails per day, and Grow at $71 a month billed annually, with 3,000 emails per day.