Email infrastructure
for AI agents
Send, receive, and route email from a single API. Your providers. Your mailboxes. One platform.
curl -X POST https://smtp.sendmux.ai/api/v1/emails/send \
-H "Authorization: Bearer smx_live_a1b2c3..." \
-H "Content-Type: application/json" \
-d '{
"from": { "email": "agent@yourapp.com" },
"to": [{ "email": "customer@example.com" }],
"subject": "Your order has shipped",
"text": "Tracking: 1Z999AA10123456784"
}'{
"ok": true,
"data": {
"message_id": "687e4c42-a36d-457f-a00a-7da2c8d93334",
"status": "queued"
},
"meta": {
"request_id": "req_xlcoz8z5sfq30x9oqya19sm9"
}
}The problem
Email tools weren't built for AI agents
No complete stack
Sending services handle outbound. Inbox providers handle receiving. You stitch together two or three services, manage separate APIs, and pay separate bills.
Not built for agents
Gmail and Outlook return full HTML email bodies that consume thousands of LLM tokens. Your agents waste compute parsing formatting instead of acting on content.
Zero provider flexibility
Current platforms lock you into their sending infrastructure. If deliverability degrades, you're stuck. No way to bring your own providers or route across multiple accounts.
Outbound sending
Your providers. Our routing.
Connect Gmail, SendGrid, Mailgun, Resend, or any SMTP-compatible provider. Not ready to configure? Send through the built-in account straight away.
Weighted distribution with automatic failover. If a provider goes down, traffic reroutes before your users notice.
Quotas at four levels: per-second, minute, hour, and day. No throttle logic needed.
Health monitoring that acts on its own. Failing providers get disabled automatically. No 3 AM pages.
HTTP API and SMTP on port 587. Drop-in compatible with any agent framework you’re already using.
import Sendmux from '@sendmux/sdk';
const sendmux = new Sendmux('smx_live_a1b2c3...');
const { data } = await sendmux.emails.send({
from: { email: 'support@yourapp.com', name: 'Support Agent' },
to: [{ email: 'customer@example.com' }],
subject: 'Your refund has been processed',
text: 'Hi Sarah, your refund of $49.00 is on its way.',
});
console.log(data.message_id);
// → "687e4c42-a36d-457f-a00a-7da2c8d93334"<!-- Raw email — 3,200+ tokens -->
<html><head><style>
.ExternalClass { width:100% }
.ReadMsgBody { width:100% }
table { border-collapse:collapse }
...847 more lines of HTML...
</style></head><body>
<table role="presentation" width="600">
<tr><td style="padding:20px">
Hi Sarah, your refund of $49.00
has been processed.
</td></tr>
...quoted thread history...
...email signatures...
...tracking pixels...
</body></html>// Sendmux response — 127 tokens
{
"extracted_text": "Hi Sarah, your refund of $49.00 has been processed.",
"from": { "email": "support@acme.com", "name": "ACME Support" },
"subject": "Re: Refund request #4821",
"thread_id": "thr_8kqm3v",
"labels": ["support", "refund"],
"received_at": "2026-04-08T09:14:22Z"
}Inbound mailboxes
Built for agents. Open to your team.
Create dedicated inboxes for your AI agents, with full visibility for your team when they need it. Receive email as clean, structured JSON. Not thousands of tokens of HTML noise.
Dedicated mailboxes on @myagent.mx or your custom domain
Clean JSON, not raw HTML. 80% fewer tokens.
Extracted text isolates new replies from quoted thread history
Labels, threads, allowlists, and blocklists. All via API.
fewer LLM tokens per email with structured parsing
How it works
From zero to sending in under five minutes
Connect your providers
Add any provider over SMTP or OAuth. Or skip this and use the built-in account.
Create agent mailboxes
Dedicated inboxes on @myagent.mx or your domain. One per agent.
Send and receive via API
HTTP API, SMTP, or both. Routing and failover are automatic.
For platform builders
Scale from one agent to thousands
Building a platform where each customer's AI agent needs email? Sendmux gives you multi-tenant isolation, granular permissions, and pricing that grows with your customers.
Multi-tenancy via teams
Each customer gets isolated inboxes, domains, providers, and API keys. Complete data isolation.
Inbox-scoped API keys
Give each agent access to only its own mailbox. Granular permissions prevent data leakage.
Role-based access control
Owner, Admin, Developer, Member. Hierarchical permissions so your team sees only what they should.
Usage-based billing that scales
No per-mailbox fees. 1,000 agent mailboxes cost nothing until emails flow. Pay for what you use.
Pricing
Pay for what you use. Nothing else.
No per-seat fees. No per-mailbox fees. No minimum commitments. Pay only when emails flow.
Included with every account:
* Email attachments are charged at $0.15 per GB.
Need dedicated infrastructure, SLAs, or volume pricing?
Talk to us about enterpriseCommon Questions