API vs SMTP: Choosing the Right Integration for Bulk Sending

Key differences

SMTP is ubiquitous and simple but can be slower and harder to scale for complex payloads. HTTP APIs offer structured requests, better error reporting, and higher throughput for programmatic sending.

When to choose API

If you need per-message metadata, webhooks, or high throughput, use the API.

When SMTP works

Legacy systems and simple transactional flows can keep using SMTP; consider pooling and rate limits.

Hybrid approaches are common: use API for new integrations and SMTP for legacy compatibility.