Sendmux

What is Sendmux?

Sendmux is the email inbox API for AI agents. It gives agents dedicated mailboxes, cleaned message content, threads, attachments, mailbox-scoped API keys, webhooks, and Server-Sent Events so agents can receive and act on email in real time. For sending, Sendmux lets teams connect Gmail OAuth, Outlook OAuth, SMTP providers, or managed Amazon SES. Delivery groups support weighted routing, sender-domain routing, per-provider quotas from per second to per day, provider health checks, and automatic failover, so teams can keep control of outbound email instead of relying on one sending provider. Developers can use the Mailbox API, Sending API, Management API, OpenAPI docs, SDKs for TypeScript, Python, Go, PHP, and Ruby, the sendmux CLI.

Key features

• Email Inbox API for AI Agents
• Dedicated Agent Mailboxes
• Mailbox History for Agent Memory
• Multi-Provider Email Sending
• Managed Amazon SES Sending
• Per-Provider Quotas and Throttling
• Weighted Routing and Failover
• Signed Webhooks and SSE Events
• MCP, SDKs, Skills, and CLI
• Usage-Based Pricing, No Mailbox Fees

Use cases

• Remember every conversation long-term memory
• Talk to systems without API
• Sign up for anything
• Email tasks to your agents
• Trigger workflows from emails