Transactional Email API with Priority Delivery
Send password resets, OTPs, receipts, and system notifications through a reliable API. Transactional emails are never throttled. They always get priority delivery, independent of domain reputation controls.
A transactional email API is a programmatic interface that lets applications send event-triggered emails like password resets, order confirmations, OTP codes, and account notifications. Unlike marketing emails sent to subscriber lists, transactional emails are initiated by individual user actions and expected by the recipient. sendmsg.io's transactional email API uses a dedicated priority queue that processes these messages separately from promotional traffic, so transactional emails are never throttled or delayed by reputation controls that may be active for marketing campaigns. The API supports REST endpoints with official SDKs for Node.js, Python, PHP, and Go, plus an SMTP relay option for drop-in integration. Every email is authenticated with SPF, DKIM, and DMARC. Delivery events including delivered, opened, clicked, bounced, and complained are streamed via webhooks for tracking and automation.
Send Your First Email
A single API call is all it takes. Choose your language and start sending.
curl -X POST https://api.sendmsg.io/v1/email/send \ -H "Authorization: Bearer YOUR_API_KEY" \ -H "Content-Type: application/json" \ -d '{"to": "[email protected]","from": "[email protected]","subject": "Your verification code","html": "<p>Your code is <strong>482910</strong></p>", "priority": "high", "tags": ["otp", "auth"] }'Full API reference with request/response schemas available in our documentation.
Priority Delivery, Never Throttled
Transactional emails are time-critical. That's why they are never throttled by domain reputation controls or sending limits. OTPs, password resets, and order confirmations always get priority delivery, regardless of what's happening with your promotional campaigns. Your domain health is still monitored, but transactional sending is never slowed down.
Priority Queue
Transactional emails bypass all reputation-based sending limits. They are routed through a dedicated priority queue that ensures sub-second processing, independent of promotional campaign volume.
Domain Health Visibility
Your sending domain still gets a live health score from 0 to 100. You can monitor bounce rates and engagement, but these signals never gate or slow your transactional delivery.
Isolated from Promotional
Transactional and promotional emails are tracked separately. Issues with a marketing campaign will never affect your OTP delivery, password resets, or order confirmations.
Built for Developers
Four ways to integrate. Pick the one that fits your stack.
REST API
Standard HTTP endpoints with JSON payloads. Works with any language or framework.
Email Templates
Reusable templates with dynamic variables. Build once, send with different data every time.
SDKs
Official libraries for Node.js, Python, PHP, and Go. Type-safe and well-documented.
Webhooks
Live event notifications delivered to your endpoint. Track every email event.
Webhook Events
Subscribe to the events that matter. Get notified as your emails move through the delivery pipeline.
Example webhook payload
{
"event": "email.delivered",
"timestamp": "2026-03-08T10:24:17Z",
"message_id": "msg_a1b2c3d4e5f6",
"recipient": "[email protected]",
"tags": ["otp", "auth"]
}email.deliveredEmail was successfully accepted by the recipient's mail server.email.openedRecipient opened the email. Tracked via a transparent pixel.email.clickedRecipient clicked a tracked link inside the email body.email.bouncedEmail was permanently rejected. The address may be invalid or inactive.email.complainedRecipient marked the email as spam. Affects sender reputation.email.deferredTemporary delivery failure. The system will retry on its own.Use Cases
Designed for the emails your users expect to arrive instantly.
OTP & Verification
Password resets, two-factor authentication codes, email verification links. Time-sensitive messages that need sub-second delivery.
Order Confirmations
Purchase receipts, shipping updates, delivery notifications. Keep your customers informed at every stage of their order.
System Notifications
Usage alerts, security warnings, downtime notices. Critical messages your users need to see and act on immediately.
Account Management
Welcome emails, password change confirmations, subscription updates. Lifecycle messages that build trust with your users.
Reliable at Scale
Infrastructure designed to handle your critical transactional volume without compromising on delivery speed or sender reputation.
Sub-second Delivery
Time-sensitive emails like OTPs are queued and dispatched within milliseconds of your API call.
Automatic Retries
Temporary failures are retried with intelligent backoff. No manual intervention needed.
Priority Queuing
Transactional emails are prioritized over bulk sends, ensuring critical messages always go first.
Delivery Logs
Full event history for every message. Search by recipient, tag, or message ID.
{
"status": "queued",
"message_id": "msg_a1b2c3d4e5f6",
"to": "[email protected]",
"priority": "high",
"estimated_delivery": "<1s",
"reputation": {
"domain_health": 94,
"protection_active": true
}
}Frequently Asked Questions
Start Sending Transactional Emails
Priority delivery, full reputation protection, and SDKs for 4 languages. Leave your email for early access.