Sendmux

Free

• Updated Jun 30, 2026, 03:29 PM

Sendmux is an email API designed specifically for AI agents, providing a unified interface for sending, receiving, routing, and reacting to email.

Use Cases ▼

Build AI agents that can send and receive emails programmatically

Automate email routing across multiple providers with failover

Parse incoming emails into LLM-friendly JSON to save tokens

Create inboxes for transactional or notification emails from AI applications

Monitor delivery events in real time for agent-driven workflows

Enable agent-to-human or agent-to-agent email communication

Integrate email capabilities into chatbots or autonomous agents

What Problem It Solves ▼

Existing email tools are not built for AI agents: they return full HTML email bodies that consume excessive LLM tokens, require stitching together separate services for sending and receiving, and lock users into a single sending provider. Sendmux solves this by offering a single API that handles inbound and outbound mail, delivers structured JSON content optimized for agents, and supports multi-provider routing to avoid vendor lock-in.

Key Features ▼

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Agent-optimized email parsing (JSON output, dramatically reduces token usage)

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Multi-provider sending with quotas, weighted routing, and failover

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Unified API for sending, receiving, routing, and real-time events

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Free tier with transparent usage-based pricing ($0.15/1k emails)

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Supports webhooks, SSE, and CLI for flexible integration

Overview

Sendmux is an email API designed specifically for AI agents, providing a unified interface for sending, receiving, routing, and reacting to email. It offers dedicated agent mailboxes, multi-provider sending with configurable quotas and failover, and live event delivery via webhooks or SSE. The API is built to optimize email for LLM consumption by stripping useless formatting, signatures, and quoted history, returning clean JSON to dramatically reduce token usage. Developers can create mailboxes on verified domains or shared domains, send emails via HTTP or SMTP, and route messages across multiple providers using weighted delivery groups. Pricing is usage-based at $0.15 per thousand emails, with no subscriptions and a free tier to get started.