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Email API for agents: send, receive, route and react to mail through one endpoint, billed per message
Sendmux is transactional email plumbing shaped for AI agents rather than newsletters. One API sends, receives, routes and fires webhooks on inbound mail, so an agent can own a real inbox address. Providers behind it include SMTP, Gmail, Microsoft 365 and Amazon SES, with failover between them, and it ships SDKs, a CLI, an MCP guide and agent skills. Pricing is pure usage with no seats or mailboxes: $0.15 per 1,000 accepted outbound recipients or inbound emails, $0.25 per 1,000 through managed Amazon SES, and $0.02 per GB-month of storage. Signup includes a managed SES route capped at 50 emails a day. No company or country is published.
Usage-only pricing with no subscription or seat fee, so there is no monthly entry price: $0.15 per 1,000 provider-accepted outbound recipients or inbound emails, $0.25 per 1,000 via managed Amazon SES, $0.02 per GB-month of storage. Free on signup up to 50 emails a day on the managed SES route. Rejected addresses are not billed.
Use tool ↗Solves a specific problem well: giving an agent an address it can send from and receive at, with routing rules and webhooks instead of a polling hack over IMAP. Provider failover across SES, Gmail and Microsoft 365 is more than most transactional APIs offer. What is missing is the vendor itself, since no legal entity, address or country appears on the site, which is a hard sell for anything handling customer mail.
Watch out: Deliverability still depends on the provider behind the route and your own domain authentication. The API does not change how mailbox providers judge you.
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