Sendmux

Sendmux provides a unified email API designed specifically for AI agents, enabling users to create agent inboxes, send emails through multiple providers, and manage routing with quotas and failover. It offers clean JSON parsing of inbound emails to reduce token usage for AI processing, supports multi-tenant teams with isolated workspaces, and flexible outbound routing through providers like Gmail, SendGrid, and SMTP. The platform is built to simplify email handling for AI agents and scale from single agents to thousands with usage-based billing and no per-seat or per-mailbox fees.

Who is it for?

Developers and companies building AI agents or platforms requiring email sending and receiving capabilities

Problem

Traditional email tools are not built for AI agents, requiring multiple services for sending and receiving, returning large HTML email bodies that waste AI compute, and locking users into single sending providers with no flexibility.

Solution

Sendmux offers a single API to send, receive, route, and react to emails with agent-shaped inboxes that provide clean JSON instead of raw HTML, flexible outbound routing across multiple providers with quotas and failover, and multi-tenant support with scoped API keys and usage-based billing.

What makes it unique

• Unified API for both inbound and outbound email tailored for AI agents
• Clean JSON parsing reduces AI token usage by up to 80%
• Flexible provider routing with weighted distribution and automatic failover
• Multi-tenant architecture with scoped API keys and team isolation

• Agent-shaped inboxes

  Create mailboxes on verified domains or shared domains with clean JSON email parsing.

  01
• Outbound email routing

  Send emails through multiple providers with weighted distribution and automatic failover.

  02
• Multi-tenant support

  Isolated teams with scoped API keys and no cross-tenant data leakage.

  03
• Usage-based billing

  Pay only for email usage with no per-seat or per-mailbox fees.

  04
• Clean JSON parsing

  Inbound emails parsed to remove signatures, quoted history, and tracking pixels to save AI tokens.

  05
• Webhooks and Server-Sent Events

  Real-time event notifications for email delivery, receipt, and spam detection.

  06
• HTTP and SMTP APIs

  Send emails via JSON over HTTPS or SMTP with the same API keys and rate limits.

  07
• Team and mailbox-scoped API keys

  Fine-grained permission control for API access per team or mailbox.

  08

Business model

SAAS

Audience

B2B

Platforms

web · api

Pricing model

subscription

Value proposition

One API for agent inboxes, BYO outbound routing, and everything in between with flexible provider control and clean JSON parsing.

Metadata

OOpen Graph

Other

CloudflareReact

Performance

PPriority Hints

UI framework

Tailwind CSS4.3.3Radix UI

UI library

Lucideshadcn/ui

Web app

PWA

Web framework

Next.js