Two Powerful Paths to Email Integration
Whether you prefer traditional SMTP with enhanced headers or a modern RESTful API, OutboundSMTP has you covered.
Try 1000 Free Credits →Enhanced SMTP with custom headers
Use standard SMTP with our custom X-Headers to unlock advanced features without changing your sending infrastructure.
Custom X-Headers
Add metadata to your emails using custom X-Headers. Track campaigns, set priorities, and control delivery behavior through SMTP headers.
Category Tagging
Organize your email streams with category tags. Separate transactional from marketing email and track performance independently.
Template Variables
Use merge tags in your SMTP messages for personalization. Dynamically replace variables at send time without pre-processing.
Delivery Options
Control delivery timing, set send windows, configure retry policies, and manage bounce handling all through SMTP headers.
# SMTP with Custom X-Headers
X-OSMTP-Category: transactional
X-OSMTP-Campaign: welcome-series
X-OSMTP-Template: onboarding-v2
X-OSMTP-Priority: high
X-OSMTP-Track-Opens: true
X-OSMTP-Track-Clicks: true
# Standard SMTP connection
Host: smtp.outboundsmtp.com
Port: 587
Auth: your-api-key
TLS: requiredModern API for full platform control
Our RESTful API gives you programmatic access to every feature of the OutboundSMTP platform.
Email Sending
Send single or batch emails via API with full control over headers, attachments, templates, and delivery options.
Subaccount Management
Create, update, and manage sub-accounts programmatically. Set limits, configure domains, and monitor usage via API.
Domain Configuration
Manage sending domains, authentication records, and custom MAIL FROM settings through the API.
Analytics & Reporting
Pull delivery reports, bounce data, engagement metrics, and aggregate statistics programmatically for custom dashboards.
# Send email via RESTful API
curl -X POST https://api.outbound.mailhop.org/v1/email/send \
-H "Authorization: Bearer YOUR_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"from": "sender@yourdomain.com",
"to": ["recipient@example.com"],
"subject": "Hello from OutboundSMTP",
"html": "<h1>Welcome!</h1>",
"category": "transactional",
"track_opens": true,
"track_clicks": true
}'Everything you need to integrate
Documentation
Comprehensive API reference with examples, guides, and tutorials to get you sending in minutes.
SDKs
Official SDKs for JavaScript, Python, PHP, Ruby, Java, and .NET. Drop-in libraries for your preferred language.
Sandbox Environment
Test your integration without sending real emails. Validate payloads, test error handling, and verify webhook processing.
API Keys
Generate and manage API keys per sub-account. Rotate keys, set permissions, and track usage independently.
Common API questions
Can I use both SMTP and the RESTful API at the same time?
Yes. Both integration methods use the same account and share your sending credits. Many customers use SMTP for their application email and the RESTful API for management and analytics.
What are the API rate limits?
Rate limits depend on your plan. All plans support burst sending, and dedicated IP plans include higher sustained throughput. Contact us for specific rate limit details for your use case.
Do you offer webhooks for delivery events?
Yes. Configure webhook endpoints to receive real-time notifications for delivery, bounce, open, click, and complaint events. Webhooks support retry logic and signature verification.
Start integrating today
Get 1,000 free email credits and full API access. No credit card required.