Sendmux

Sendmux provides an email API designed for AI agents and products to send, receive, route, and monitor email from a single endpoint. It supports using your own SMTP or OAuth-based providers, while delivering inbound mail to dedicated agent inboxes that return parsed JSON. The system emphasizes actor inboxes and tooling around multi-tenant teams, making it suitable for teams operating email for customers’ agents.

The tool offers both outbound sending and inbound mailbox management with a unified API surface. It can route and monitor deliveries, manage quotas, and track health across multiple providers. Agents can leverage built-in accounts or connect external sending services, and the documentation describes various surfaces such as REST, SSE, IMAP, and SMTP.

Sendmux exposes management for teams, mailboxes, keys, and billing, and provides API references for Sending, Management, and Mailbox APIs. It outlines how to create agent inboxes, connect providers, and monitor delivery, with guidance on webhooks, events, and signing to ensure trust in payloads.

The product page outlines plans, platform capabilities, and integrations, noting a Free tier and Pro tier with usage-based pricing and enterprise options. It also discusses multi-tenant isolation, mailbox and domain management, and the ability to scale from one agent to thousands, with tenant isolation and per-team quotas.

Use cases

• AI agents or products that need email send/receive with real inboxes
• Teams managing multiple agent mailboxes with visibility and control