What is Sendmux AI?
Sendmux AI is a unified email API designed specifically for AI agents, combining outbound sending and inbound inbox management into a single platform. It eliminates the complexity of stitching together separate services for sending and receiving, allowing developers to create agent inboxes, route outbound emails through their own providers, and automatically fail over between providers—all from one API.
Key features include dedicated mailboxes on verified domains or the shared myagent.mx domain, with the ability to receive emails as clean, structured JSON. This reduces token consumption for LLMs by stripping HTML formatting, signatures, and quoted history, extracting only the new reply content. Labels, threads, allowlists, and blocklists are fully manageable via API, giving each agent its own inbox while providing fleet-wide visibility.
For outbound sending, Sendmux AI supports connecting Gmail, SendGrid, Mailgun, Resend, or any SMTP-compatible provider. Developers can set provider weights and quotas to control traffic distribution, ensuring delivery boundaries are respected. Automatic failover ensures high reliability if a provider experiences issues.
Use cases include AI-powered customer support agents that need to send and receive emails, automated email workflows for sales or marketing, and any application requiring scalable email handling with minimal overhead. Technical details include HTTP and SMTP support for sending, with mailbox credentials acting as both Bearer tokens and SMTP passwords. Delivery events are available via signed webhooks for server-side processing, SSE for live mailbox clients, and typed change polling for state resynchronization.
Sendmux AI solves the problem of fragmented email infrastructure, reducing costs and complexity while optimizing email processing for AI agents.
Use Cases
Key Features
unified email API outbound sending inbound inbox management structured JSON extraction provider failover dedicated mailboxes label and thread management allowlist/blocklist control provider weight and quota automatic failoverWho is it for?
AI developers, LLM engineers, platform teams, DevOps engineers, SaaS builders, email API integrators
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