Sendmux

Sendmux helps developers give AI agents a real email identity. Instead of stitching together a sending API, mailbox provider, parser, webhook layer, and billing system, teams can use one platform for inbound mailboxes, outbound sending, routing, quotas, webhooks, and live inbox events.

Agents can receive email in dedicated mailboxes, read messages and threads, process attachments, send replies, and stream inbox activity through Server-Sent Events. Outbound sending supports SMTP, Gmail OAuth, Outlook OAuth, and Sendmux-managed Amazon SES, with delivery groups, weighted routing, per-provider quotas, health checks, and failover.

Sendmux is built for AI agent teams, automation agencies, SaaS platforms, and developers building support agents, sales agents, scheduling agents, monitoring agents, and workflow agents. It also includes REST APIs, OpenAPI specs, SDKs, CLI, MCP tools, and Sendmux Skills.

How To Use Create a Sendmux team, then create an agent mailbox using the included myagent.mx domain or a verified custom domain. Connect SMTP, Gmail OAuth, Outlook OAuth, or managed Amazon SES for outbound sending. Generate team-level or mailbox-scoped API keys, then use the API, SDKs, CLI, MCP, or Sendmux Skills to send, receive, route, and monitor email. Subscribe to webhooks or Server-Sent Events to watch live inbox and delivery events.

Core Features
Email inbox API for AI agents Dedicated agent mailboxes Multi-provider email sending Managed Amazon SES sending Per-provider quotas and throttling Weighted routing and failover Signed webhooks and SSE events Mailbox API for threads and attachments MCP, SDKs, CLI, and Sendmux Skills Usage-based pricing with no mailbox fees

Use Cases
AI customer support agents with real inboxes Sales and outreach agents using customer-owned providers Scheduling and executive-assistant agents Research and monitoring agents that process email updates Ops, finance, and vendor workflow agents Multi-tenant SaaS platforms needing isolated mailboxes Automation agencies managing client email workflows Internal tools that need webhook-driven email automation