Sendmux.ai
Sequenzy
MailChimp
Robotomail
Klaviyo
Customer.io
Mails.ai
Resend
api-usage
Sendmux is the email inbox API for AI agents. Give an agent its own mailbox, then let it receive email, read threads, inspect attachments, send replies, and react to new messages as they arrive. Each mailbox can return cleaned message content for agents, raw email when needed, signed webhooks, and Server-Sent Events for live inbox updates.
Hereโs where it helps: teams can use Sendmux for both inbound agent mailboxes and outbound email sending. Connect Gmail OAuth, Outlook OAuth, SMTP providers, or managed Amazon SES, then route mail through delivery groups with weighted routing, sender-domain routing, provider health checks, automatic failover, and quotas from per second to per day. That gives builders more control than a single-provider sending setup.
For inbound workflows, Sendmux supports custom domains with SPF, DKIM, and DMARC, mailbox-scoped API keys, sender filters, folders, labels, attachments, raw .eml downloads, IMAP retrieval, and SMTP submission. Agents can watch inbox activity through SSE, receive webhook events, or query messages and threads through the Mailbox API.
Developers can work with the Sending API, Mailbox API, Management API, OpenAPI docs, SDKs for TypeScript, Python, Go, PHP, and Ruby, the sendmux CLI, or MCP tools. Teams also get tenant isolation, provider setup, domains, logs, metrics, billing, usage tracking, and delivery history in one place.
Sendmux fits AI agent products, automation agencies, support agents, scheduling agents, ops workflows, platform builders, and controlled BYO-provider cold email setups that want to send from AI tools. Pricing is usage-based, with no per-seat fees, no per-mailbox fees, and standard email priced at $0.15 per 1,000 messages.
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Sendmux.ai's answer
Publicly, Sendmux is built around REST and OpenAPI APIs, SMTP, IMAP, signed webhooks, Server-Sent Events, Model Context Protocol, SDKs for TypeScript, Python, Go, PHP, and Ruby, the sendmux CLI, and installable Sendmux Skills for agent workflows.
Sendmux.ai's answer
Sendmux combines an email inbox API for AI agents with multi-provider outbound sending. Agents get dedicated mailboxes, mailbox-scoped API keys, cleaned message content, threads, attachments, signed webhooks, SSE live inbox events, and sending through Gmail OAuth, Outlook OAuth, SMTP, or managed Amazon SES with quotas, weighted routing, and failover.
Sendmux.ai's answer
Choose Sendmux if you need both inbound agent mailboxes and outbound provider control. Sending-only APIs do not give agents a real inbox, and mailbox-first tools usually do not offer bring-your-own-provider routing, per-provider quotas, and failover. Sendmux gives teams one control plane for inboxes, sending, events, providers, logs, domains, billing, MCP, SDKs, Skills, and CLI access.
Sendmux.ai's answer
Sendmux is built for AI agent product teams, automation agencies, and platform builders that need agents to send, receive, route, and react to email in production. It also fits teams using their own Gmail, Outlook, or SMTP providers for controlled outbound and cold email workflows from AI tools.
Sendmux.ai's answer
Sendmux came from a simple problem: production AI agents need real email, not a hacked shared inbox. Teams were stitching together sending providers, mailboxes, parsers, webhook services, routing logic, and billing. Sendmux puts agent email identity, inbound mail, outbound sending, live events, and provider control into one API-first platform.
Sendmux.ai's answer
Target Markets, CFC, Aurora Capital
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Customer.io - We make it easy to send emails triggered by user behavior. Build, measure and improve your emails to activate and retain users
Mails.ai - Maximize Email Impact with Mails.ai: Elevate your email sending through AI-driven campaigns, sender rotation, free unlimited email warmup, email verification, and outstanding ROI, catering to the modern marketer's needs.
