Lumbox
Email & MarketingEmail infrastructure API for AI agents to create inboxes, extract OTPs, verification links, and send/reply programmatically.
Lumbox (formerly AgentMailr) is an API-first email infrastructure platform designed exclusively for AI agents and autonomous systems. It allows agents to programmatically create real email inboxes, automatically extract OTPs and verification links, and send/reply/forward emails through a simple REST API or Model Context Protocol (MCP) tools. Key differentiators include long-polling endpoints that block until emails arrive, regex-based OTP extraction returning clean JSON, prompt injection defense with boundary markers, and first-class MCP support for Claude Code, Cursor, and Windsurf. The platform is optimized for browser automation, agent-to-human communication, and email-based authentication flows.
Best for
AI/ML engineers and GTM teams building autonomous agents that need programmatic email capabilities for verification flows, account creation, and agent-to-human communication.
Last updated: March 19, 2026
25/50
Overall Score
API Quality
9/10
GTM Relevance
16/20
PricingFreemium
Complexityeasy
Learningeasy
Visit agentmailr.com →API Analysis
REST API
✓
Available
Webhooks
✓
Available
GraphQL
—
—
OAuth
—
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Pricing
freemiumFree Tier
Free tier: 3 inboxes, 500 received/100 sent emails. Paid plans from $9/mo (10 inboxes) to $99/mo (250 inboxes). Overages: $0.50 per 1K emails.
Strengths & Weaknesses
Strengths
Automatic OTP and verification link extraction eliminates need for agents to parse raw HTML, returning clean structured JSON
Long-polling endpoints (/wait and /otp) remove need for complex polling loops, simplifying agent implementation
First-class Model Context Protocol (MCP) support with 40+ tools for seamless integration with Claude Code, Cursor, and Windsurf
Prompt injection defense with boundary markers protects LLMs from malicious email content
Predictable pricing model based on inboxes rather than email volume, with generous free tier for testing
Weaknesses
Relatively new product (recently rebranded from AgentMailr) with limited production use cases and community
Limited to email use cases only - no broader communication channels like SMS or voice
Custom domain setup requires DNS configuration which may be complex for non-technical users
SDKs still marked as 'coming soon' for Python and TypeScript despite being advertised
Alternatives
Reviews
Links
FAQ
What is Lumbox?
Lumbox (formerly AgentMailr) is an API-first email infrastructure platform designed exclusively for AI agents and autonomous systems. It allows agents to programmatically create real email inboxes, automatically extract OTPs and verification links, and send/reply/forward emails through a simple REST API or Model Context Protocol (MCP) tools. Key differentiators include long-polling endpoints that block until emails arrive, regex-based OTP extraction returning clean JSON, prompt injection defense with boundary markers, and first-class MCP support for Claude Code, Cursor, and Windsurf. The platform is optimized for browser automation, agent-to-human communication, and email-based authentication flows.
Is Lumbox free?
Yes, Lumbox offers a free tier. Free tier: 3 inboxes, 500 received/100 sent emails. Paid plans from $9/mo (10 inboxes) to $99/mo (250 inboxes). Overages: $0.50 per 1K emails.
What are Lumbox alternatives?
Popular alternatives to Lumbox include Resend, SendGrid, Mailgun, Postmark, Zapier, Make, Pipedream. Compare features, API quality, and pricing on GTM Tools.
Does Lumbox have an API?
Yes, Lumbox provides a REST API. API quality is rated EXCELLENT. Documentation: https://docs.lumbox.co.
Who is Lumbox best for?
AI/ML engineers and GTM teams building autonomous agents that need programmatic email capabilities for verification flows, account creation, and agent-to-human communication.