Deliver one-time verification passwords in under 2 seconds guaranteed
When customers wait for an OTP code, every second of latency kills login conversion. Dispatch 2FA and TOTP challenge codes through priority low-latency transactional IP queues.
Drop into your application in under 60 seconds
Native typed interfaces with zero unnecessary dependencies. Built for standard fetch and modern edge runtimes.
import { SadaSend } from 'sadasend';
const sadasend = new SadaSend(process.env.SADASEND_API_KEY!);
export async function dispatchLoginOtp(userEmail: string, otpCode: string) {
return await sadasend.emails.send({
from: 'security@yourdomain.com',
to: userEmail,
subject: `Your Verification Code: ${otpCode}`,
html: `
<div style="font-family: sans-serif; text-align: center; padding: 24px;">
<h2>Your 6-Digit Verification Code</h2>
<div style="font-size: 32px; font-weight: 700; letter-spacing: 6px; color: #10b981; margin: 20px 0;">
${otpCode}
</div>
<p style="color: #64748b; font-size: 14px;">Valid for 5 minutes. Do not share this code.</p>
</div>
`,
tags: ['auth-otp', '2fa-challenge'],
headers: { 'X-Priority': '1', 'Precedence': 'bulk' }
});
}Engineered for high deliverability and zero incident risk
Every layer from edge connection pooling to per-key rate limits is designed to keep critical transactional dispatches fast, reliable, and contained.
Priority Edge Queues
OTP and 2FA dispatches are routed through isolated priority delivery queues, bypassing bulk marketing traffic and avoiding delivery lags.
Anti-Prefetch Headers
Security headers prevent enterprise email security scanners (e.g. Mimecast, Proofpoint) from invalidating single-use OTP tokens before users see them.
Real-Time Delivery Confirmation
Synchronous API response returns in under 20ms with message UUID, allowing your auth UI to confirm dispatch to the user immediately.
Domain Reputation Protection
High reputation IP pools and aligned DKIM signatures guarantee primary inbox placement in Gmail, Outlook, Apple Mail, and Yahoo.
SadaSend vs Shared Marketing Senders
Sending OTP codes via marketing email providers puts security codes in the spam or promotional tab. SadaSend uses dedicated transactional IP routes.
| Feature & Capability | SadaSend | Shared Marketing Senders |
|---|---|---|
| Average Inbox Delivery Speed | < 2 seconds | 15 - 90 seconds (Queue delay) |
| Dedicated Transactional IPs | ||
| Anti-Scanner Defense Headers | ||
| low-latency Synchronous API |
Start with 3,000 emails every month at zero cost
No artificial paywalls on security. Unlike legacy providers that reserve recipient allowlists or dedicated IP pools for high enterprise tiers, every SadaSend account receives full safety controls from day one.
Everything you need to know about OTP email API
Clear, transparent answers on deliverability, API authentication, and rate limits.
Related developer guides and architectural tutorials
Explore step-by-step production implementation blueprints, benchmarks, and protocols.
REST API Reference & Endpoints
Complete REST API reference for sending emails, managing API keys, tracking delivery events, and configuring recipient allowlists with low latency.
Official Client SDKs (TypeScript & Python)
Official zero-dependency client SDKs for SadaSend. TypeScript and Python packages are live on npm and PyPI with typed results and auto-idempotency.
API Error Codes & Troubleshooting
HTTP status codes, machine-readable error reasons, and step-by-step remediation guides for API key rate limits, circuit breakers, and bounce handling.
Email Threat Modeling for SaaS: Preventing Compromised API Key Abuse
What happens when an engineer accidentally commits an email API key to a public GitHub repo? Here is the threat model and defense blueprint.
Why your transactional email goes to spam
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SPF, DKIM and DMARC: what each one actually does
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Building a transactional email queue on Bun and BullMQ without losing messages
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