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.