Email Inbox + Sending API for AI Agents

Sendmux is an email API built for AI agents and the teams that run them. It combines inbound mailboxes, outbound sending, routing controls, and delivery events in one API surface, so developers do not need to stitch together separate inbox and sending services. The product is designed for agent workflows where raw HTML email is expensive or awkward to process, and where provider flexibility matters if deliverability changes.

The platform lets you create dedicated agent mailboxes on verified domains or on the shared myagent.mx domain. Incoming mail can be read as clean structured JSON instead of raw HTML, with signatures and quoted history stripped by default. When needed, links, headers, attachment metadata, and raw messages are also available. The inbox experience supports thread handling, labels, allowlists, blocklists, bulk actions, drafts, and keyboard-driven navigation for teams monitoring many agent inboxes.

For sending, Sendmux connects to Gmail, SendGrid, Mailgun, Resend, any SMTP-compatible provider, or a built-in account. Routing supports weighted distribution, per-second/minute/hour/day quotas, automatic failover, and provider health monitoring that can disable failing providers. The API is available over HTTP and SMTP on port 587, making it compatible with existing agent frameworks.

It also includes multi-tenancy for platform builders, with isolated workspaces for customers, inbox-scoped API keys, and tenant-scoped data, quotas, and routing. Pricing is usage-based, with no per-seat fees and no per-mailbox fees.

Key features:
- Dedicated agent mailboxes on verified domains or shared myagent.mx
- Structured email parsing with signatures and quoted history stripped by default
- Unified sending, receiving, routing, and delivery events through one API
- Provider routing with weighted distribution, quotas, and automatic failover
- HTTP API and SMTP support for outbound mail
- Multi-tenant workspaces with inbox-scoped API keys and tenant isolation
- Keyboard-driven unified inbox with search, labels, drafts, and bulk actions