SendPorterDeveloper-First Email Infrastructure
Transactional Email API Built for Speed & Inbox Placement
Deliver password resets, 2FA verification codes, order confirmations, and urgent alerts with sub-50ms API response times. 100% DKIM-signed, tracked like a parcel, and protected from shared IP pool contamination.
2,500 free emails monthly · REST API + SMTP Relay · Automated 2048-bit DKIM · Webhooks
Form 01 — Quickstart
Integrate in Under 60 Seconds
Send your first transactional email with a single HTTP POST request. No cumbersome multi-step setup or vendor lock-in.
- Sub-50ms HTTP intake returning instant
202 Accepted - Official SDKs for Node.js, Python, and PHP
- SMTP relay on port 587 with STARTTLS for WordPress, Django, Laravel, and Rails
- HMAC-SHA256 signature headers on every webhook event
# one request, one delivered email
curl -X POST https://sendporter.com/v1/mail/send \
-H "Authorization: Bearer $SENDPORTER_API_KEY" \
-d '{
"from": "Orders <orders@yourdomain.com>",
"to": ["customer@example.com"],
"subject": "Your order shipped",
"html": "<h1>It's on the way!</h1>"
}'
# → {"message_ids": ["f7d26efa-…"]}
Infrastructure Highlights
Everything Your Transactional Pipeline Needs
Built from the ground up in Go for ultra-low latency, cryptographic certainty, and zero IP contamination.
Sub-50ms REST API Intake
Your application thread never waits for external SMTP handshakes. SendPorter acknowledges incoming mail payloads in under 50ms with a guaranteed tracking identifier.
Automated 2048-Bit DKIM Signing
Every message is signed with a dedicated 2048-bit RSA key generated specifically for your sending domain, ensuring 100% compliance with Gmail and Yahoo standards.
Authenticated SMTP Relay
Drop-in replacement for existing software. Point WordPress, Magento, Laravel, or Django at sendporter.com:587 and authenticate using your API key.
Parcel-Style Delivery Manifests
Track every email like a physical parcel: queued, signed, relayed, delivered, opened, and clicked with millisecond timestamps and upstream SMTP diagnostic codes.
HMAC Webhooks & Idempotency
Receive cryptographically signed delivery receipts directly to your server endpoints. Built-in retry schedules ensure you never miss a bounce or delivery event.
Automated Suppression Guardian
Hard bounces (5xx codes) and spam complaints automatically populate your suppression list, preventing bad email addresses from harming your domain reputation.
Exponential Backoff Retries
When receiving MX servers throttle or graylist incoming messages (4xx codes), our delivery worker backs off with intelligent jitter to preserve IP reputation.
Bring-Your-Own-Cloud (SES)
Connect your sending domain directly to its own AWS account and SES identity. Enjoy complete isolation from every other sender on the internet.
Benchmark Comparison
How SendPorter Compares to Legacy Email APIs
Designed for developer velocity, transparent pricing, and verifiable delivery receipts.
| Capability | SendPorter | Twilio SendGrid | Mailgun | Postmark |
|---|---|---|---|---|
| API Intake Latency | < 50ms | 150ms – 400ms | 120ms – 300ms | < 100ms |
| Delivery Visibility | Full Parcel Manifest (SP-YYYY-XXXX) | Opaque event logs | Basic log history | Activity logs |
| DKIM Key Generation | Automated 2048-bit RSA | Manual / Shared CNAME | Manual DNS setup | Automated DKIM |
| Free Monthly Quota | 2,500 emails/mo | 100 emails/day cap | Trial only (30 days) | 100 emails total |
| 50k Monthly Emails | $29 / month | $34.95 / month | $35.00 / month | $55.00 / month |
| Shared IP Contamination | Isolated Domain Reputation | High (Massive pools) | High (Shared pools) | Isolated transactional |
| HMAC-Signed Webhooks | Included on all tiers | Requires custom config | Included | Included |
Developer Use Cases
Engineered for High-Priority Application Events
Transactional messages that directly impact user activation, security, and revenue.
Authentication & 2FA
One-time passcodes (OTP), magic sign-in links, and password resets delivered within milliseconds so users are never stuck waiting on login screens.
E-Commerce & Billing
Order confirmations, shipping notifications with live courier links, invoice PDFs, and subscription renewal receipts with verifiable audit logs.
Security & Alerting
Suspicious login alerts, password change confirmations, API threshold notifications, and database backup reports that must never get caught in spam.
Frequently Asked Questions
Everything You Need to Know About Our Transactional Email API
What is a transactional email API?
A transactional email API is an HTTP REST service that lets software applications trigger programmatic, automated emails in response to user actions. Common examples include password reset links, order confirmations, verification PINs, and security alerts. Transactional APIs differ from marketing tools by focusing on sub-second dispatch speeds and near-100% inbox deliverability.
How does a transactional email API differ from marketing email services?
Marketing email platforms are designed for batch sending newsletters and promotional campaigns to large subscriber lists, which often trigger bulk categorization. Transactional email APIs deliver urgent, 1-to-1 operational emails that users explicitly request. Because transactional emails carry critical user data, they must bypass promotional tabs and land directly in the primary inbox.
How fast does SendPorter deliver transactional emails?
SendPorter processes API requests and returns an HTTP 202 Accepted code in under 50 milliseconds. Once accepted, the message is signed with your domain's 2048-bit DKIM key and relayed to the recipient's MX server (such as Gmail, Outlook, or Apple Mail) within milliseconds.
Can I send using standard SMTP instead of the REST API?
Yes. SendPorter includes an authenticated SMTP submission server on port 587 with STARTTLS encryption. You can use your API key as the password in any SMTP client, including PHPMailer, Nodemailer, WordPress, Django, Laravel, and Ruby on Rails. Both SMTP and REST API submissions share the exact same DKIM signing, delivery queue, and event tracking pipeline.
How does SendPorter ensure compliance with Google and Yahoo 2024–2026 rules?
Google and Yahoo enforce strict requirements: all high-volume senders must have valid SPF and DKIM authentication, aligned DMARC policies, low spam complaint rates (< 0.3%), and one-click unsubscribe support. SendPorter enforces alignment automatically and isolates domain reputations so your delivery is never compromised by external senders.
How do webhooks work with the transactional email API?
SendPorter dispatches real-time HTTP POST webhooks to your server for 9 events: queued, signed, relayed, delivered, bounced, deferred, opened, clicked, and suppressed. Each webhook payload includes an HMAC-SHA256 signature header so your server can verify authenticity.
Start sending with the modern transactional email API
2,500 free emails every month. Sub-50ms API response, automated DKIM, and parcel delivery receipts.
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