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Sendmux is an email inbox API for AI agents to send, receive, route, and react to email via Gmail, Outlook, SMTP, or Amazon SES.
Sendmux is an email inbox API for AI agents to send, receive, route, and react to email via Gmail, Outlook, SMTP, or Amazon SES. It provides dedicated agent mailboxes so each agent can have its own real email identity for reading threads, processing attachments, sending replies, and responding to inbox activity.
For outbound delivery, Sendmux offers a single API surface that routes messages through the team’s chosen providers. It supports delivery groups with weighted routing, sender-domain routing, health checks, automatic failover, and per-provider quotas, along with delivery logs and metrics for visibility.
Get an agent mailbox
Follow the setup instructions to create a Sendmux agent inbox and obtain the credentials needed for that mailbox.
Use the APIs for inbox actions
Call the Mailbox and Sending APIs to read threads, process attachments, and send replies from the agent mailbox.
Configure routing and events
Set up delivery routing with quotas and failover, then handle inbox activity using signed webhooks or Server-Sent Events.
Sendmux is designed for developers building AI email agents and agent platforms that need inbound mailbox access plus outbound sending control across multiple providers. It also fits teams that require routing controls, tenant isolation, and mailbox-scoped access for multiple agents.