What is Sendmux AI?

Sendmux is a unified email inbox API for AI agents that handles inbound, outbound, routing, and delivery events; site pages render main content without JavaScript.Developer-focused features include agent-shaped mailboxes, verified domains, and endpoints that return raw and cleaned JSON email bodies (text, HTML, links, headers, attachment metadata) to reduce LLM token consumption and simplify parsing.

Routing controls support provider weights, quotas (second/minute/hour/day), delivery groups and failover to route traffic across multiple sending providers without provider lock-in.Outbound sending supports HTTP and SMTP, idempotency keys for safe retries, text/HTML bodies, custom headers, and attachment support.

Realtime integrations include signed webhooks and Server-Sent Events (SSE) for delivery, receipt, and spam notifications so agents and clients can react without polling.API surface includes mailbox message content endpoints, batch actions, event streams, and delivery events for automating inbox workflows and improving deliverability and routing management.

Sendmux AI on the web:

Sendmux AI details

Company: Jonah and Associates Pty Ltd
Jurisdiction: Victoria, Australia
Built for: Developers
Data residency: European Union
Stated compliance: GDPR

Compliance as stated in Sendmux AI's own published documentation.

Sendmux AI tech specs

Works with: OpenAI / GPT Anthropic / Claude
Integrations: Google Workspace

Sendmux AI pricing

Freemium

Mailbox storage $0.02 per gb/mo

Standard email $0.15 per 1000 emails

Managed amazon ses $0.25 per 1000 emails

$0.02/mo is cheaper than most for Email median $20/mo

Most Email tools start between $9.99 and $39 a month.

Auto-renewal: Yes

Trial, refund and renewal terms as stated in Sendmux AI's own published documentation.

Verify on the official pricing page.

View plans

Sendmux AI's 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, and CLI
Usage-Based Pricing, No Mailbox Fees

Sendmux AI use cases

Long-Term Agent Email Memory - Use the Mailbox API to let agents retrieve past threads, attachments, cleaned message text, and raw email history, then answer with context from every message available to that agent mailbox.
Multi-Provider Email Sending - Send email through Gmail OAuth, Outlook OAuth, SMTP providers, or managed Amazon SES, with weighted routing, failover, and per-provider throttling by second, minute, hour, and day.
Live Agent Inbox Events - Connect agents through MCP, SDKs, CLI, webhooks, and Server-Sent Events so they can receive live inbox events, inspect mailbox activity, and act on new email in real time.