SMTP.com is a reliable email relay API and delivery platform, offering scalable plans from $25/month for 50k emails.
Free·from $25/mo
About Sendmux
What is Sendmux?
Sendmux is an email API built specifically for AI agents. It lets you create agent inboxes, send emails through your own providers, and route messages with quotas, weighted delivery, and failover—all from a single API. It supports MCP, SDK, and CLI, making it easy for AI agents to send and receive email programmatically.
Problem it solves
Traditional email APIs are designed for human workflows, not AI agents. Sendmux solves the challenges of giving agents a persistent inbox, managing sending quotas, and handling provider failover. It simplifies email integration for AI developers, reducing the complexity of building email capabilities into agents.
Who is it for?
Sendmux is for developers and teams building AI agents that need to send or receive email (e.g., customer support bots, automated assistants). It's not for marketers looking for a bulk email marketing platform; it's a developer tool for programmatic email.
Real use cases
Use Sendmux to give your AI agent an inbox where it can receive and reply to emails, automate responses, or send notifications. It's used with frameworks like LangChain, Claude Code, and OpenClaw, and supports multiple programming languages.
Key features
- Agent inboxes — Create dedicated email inboxes for your AI agents to receive and manage messages.
- Multi-provider sending — Send through your own email providers, with quotas, weighted delivery, and failover.
- MCP support — Connect via Model Context Protocol for seamless agent integration.
- SDK & CLI — Available for TypeScript, Python, and CLI for easy automation.
- Usage-based pricing — Pay only for accepted recipients and inbound emails, no seat or mailbox fees.
- Delivery logs & metrics — Track sending activity, usage, and team-level isolation.
SaaSpartout Score
7.5
/10
Editorial score from our review methodology — not user ratings.
◆ AI advisor — 30 seconds, no signup
Why are you looking at Email & Fax tools today?
Sendmux Pricing
Sendmux pricing: from $0.15/1k recipients.
For comparison: the median starting price in Communication is $15.99/month, measured across 153 tools we track. See the full SaaS Pricing Index →
Standard usage
$0.15 per 1,000 accepted recipients or inbound emails. No seats, no mailbox fees, no minimums.
Managed Amazon SES
$0.25 per 1,000 accepted recipients when using the built-in account. Includes a free sending account with 50 emails/day cap on sign-up.
Mailbox storage
$0.02 per GB per month, metered across all team mailboxes.
Enterprise
Custom pricing with dedicated infrastructure, priority support, volume pricing, and SLAs.
Free to start, no credit card required.
Frequently asked questions
How much does Sendmux cost?
Sendmux charges $0.15 per 1,000 accepted recipients or inbound emails (standard usage). Managed Amazon SES is $0.25 per 1,000 recipients, and mailbox storage is $0.02 per GB per month. There are no seat fees or minimums. You can start for free with a daily cap of 50 emails.
Is Sendmux free?
Sendmux is free to start. You get a managed Amazon SES route with a cap of 50 emails per day, and you only pay when you exceed that or use additional features. No credit card is required to sign up.
What is Sendmux used for?
Sendmux is an email API designed for AI agents. It allows agents to have their own inboxes, send emails through providers, and route messages with quotas, weighted delivery, and failover. It's used by developers integrating email into AI assistants, chatbots, and automated systems.
Does Sendmux integrate with LangChain or Claude?
Yes, Sendmux offers SDKs for TypeScript, Python, and CLI, and supports MCP (Model Context Protocol). It works with frameworks like LangChain and tools like Claude Code, OpenClaw, and AI SDK.
Who is Sendmux best for?
Sendmux is best for developers and teams building AI agents that need to send and receive email programmatically. It's ideal for customer support bots, automated assistants, and any agent that requires a persistent email inbox. It's not designed for traditional email marketing campaigns.
What are the alternatives to Sendmux?
Alternatives include other email APIs like SendGrid, Postmark, or Amazon SES (which Sendmux can use as a provider). However, Sendmux focuses specifically on AI agents, offering features like agent inboxes and MCP integration that general-purpose email APIs lack.
