What is Sendmux CLI?

Give Every AI Agent a Real Email Address
Sendmux is built for teams shipping AI agents that need to work over email. Not just send a message once. Actually receive replies, read threads, process attachments, react to new mail, and keep a durable email identity in production.

Email Inbox API for Agents
Each agent can have its own mailbox on the included myagent.mx domain or a verified custom domain. The Mailbox API lets agents read messages, threads, folders, attachments, identities, usage, quotas, and mailbox metadata. They can also send, reply, reply-all, and forward from that mailbox.

For event-driven workflows, Sendmux supports signed webhooks and Server-Sent Events. That means an agent can react when new mail arrives instead of polling an inbox over and over.

Sending Built In
Sendmux covers outbound sending too. Teams can send through Gmail OAuth, Outlook OAuth, their own SMTP providers, or Sendmux-managed Amazon SES. Delivery groups let teams split traffic across providers, set weights, apply sender-domain routing, enforce quotas, and fail over when a provider becomes unhealthy.

Built for Product Teams
Sendmux includes team isolation, scoped API keys, dashboard roles, delivery logs, metrics, billing controls, OpenAPI specs, SDKs for TypeScript, Python, Go, PHP, and Ruby, plus a CLI for terminal workflows.

Usage-Based Pricing
Sendmux does not charge per seat or per mailbox. Teams pay for usage: incoming email, outgoing email, managed Amazon SES sending, and mailbox storage. This fits agent products where the number of agents, customers, or workspaces can grow before message volume does.

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Sendmux CLI's key features

Webhook setup and management with HTTPS endpoints for email delivery and mailbox events
Configurable event-type selection and scoping of webhooks to teams or specific mailboxes
Signature verification using x-sendmux-signature with signing-secret rotation
Management API to create webhooks, list delivery attempts, fetch retained payloads, rotate secrets, and send test events
Mailbox API with a mailbox client using server-sent events (SSE) for low-latency live message streams

Sendmux CLI use cases

Route inbound emails to your app by configuring secure HTTPS mailbox webhook endpoints with event filtering and rotating-secret signature verification, while relying on retry/dedup tracking and 7-day payload retention to ensure reliable processing and easy debugging
Power real-time support and notification systems using Sendmux live SSE mailbox streams and delivery attempt analytics to trigger instant alerts, debug failed deliveries, and automatically retry transient errors
Create compliant audit and forensic workflows by capturing mailbox events for 7 days, verifying webhook signatures, and using delivery/dedup logs and delivery debugging to reconstruct message delivery timelines and prove integrity