Sendmux

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About Sendmux

Sendmux is an email API and inbox service designed for AI agents and agent platforms, enabling them to interact with email in a structured, agent-friendly way. It provides dedicated inboxes on shared or custom domains, allowing teams to create mailboxes for support bots, sales agents, schedulers, or monitoring agents without managing separate SMTP, inbox, or routing tools. The service handles sending and receiving emails across multiple providers, returning messages as clean JSON instead of heavy HTML, which simplifies integration for AI-driven workflows. The platform includes a unified inbox dashboard where users can view all agent inboxes in a single interface, search across mailboxes, label threads, and perform bulk actions. Human operators can also step into conversations when needed, bridging the gap between automated agents and manual oversight. Sendmux abstracts the complexity of email infrastructure, providing a production-ready solution for teams that need reliable, scalable email interactions for their AI agents.

Key features

Agent-shaped inboxes
Unified inbox dashboard
Provider-agnostic outbound routing
Multi-tenant teams and scoped keys
Live events via webhooks and SSE
AI-native tooling and MCP server

Use cases

Support bots for customer support leaders
Sales agents for sales and growth engineers
Scheduling agents for internal scheduling needs

Pros

Provides dedicated, agent-shaped inboxes on shared or custom domains for AI agents
Returns messages as clean JSON with signatures, quoted history, links, headers, and attachment metadata handled
Supports unified sending and receiving across multiple email providers with failover and weighted delivery
Offers a single API surface for outbound mail, inbound mailboxes, routing controls, and delivery events
Includes SDKs, CLI, and MCP integration for seamless agent workflows

Cons

Requires setup of agent inboxes and API keys, which may involve initial configuration overhead
Limited to email-based interactions, excluding other communication channels
Dependency on third-party email providers for sending, which may introduce deliverability constraints

Frequently asked questions about Sendmux

What is Sendmux and who is it designed for?

Sendmux is an email API and inbox service designed specifically for AI agents and agent platforms. It provides real inboxes on shared or custom domains, handles sending and receiving across multiple providers, and returns messages as clean JSON for easier processing by agents.

How does Sendmux handle email sending and receiving for AI agents?

Sendmux offers a unified API surface for outbound mail, agent mailboxes, routing controls, and delivery events. It allows agents to send emails without provider lock-in, receive messages as structured JSON, and manage inboxes through a single dashboard.

Can Sendmux integrate with existing AI agent frameworks?

Yes, Sendmux provides SDKs, CLI tools, and MCP (Model Context Protocol) endpoints for integration with frameworks like LangChain, AI SDK, and OpenClaw. It also supports direct API key authentication for sending and receiving emails.

Does Sendmux support custom domains for agent inboxes?

Yes, Sendmux allows creating agent inboxes on verified custom domains or the shared myagent.mx domain. This provides flexibility in branding and domain management for agent communications.

What are the key features of Sendmux for AI agents?

Key features include agent-shaped inboxes, unified inbox dashboard, support for multiple providers, clean JSON message handling, routing controls, weighted delivery, failover mechanisms, and batch message actions.

How do I get started with Sendmux?

To get started, create an agent inbox by following the instructions on the Sendmux website, install the Sendmux skills or SDK, and configure your API keys for sending and receiving emails. Detailed setup guides and documentation are available on the Sendmux site.