Category
Transactional Email APIs pricing
Transactional Email APIs send programmatic, event-triggered mail (receipts, password resets, magic links, notifications) over REST/SMTP with webhooks for delivery events. The category splits into proven incumbents optimized for scale and deliverability (SendGrid, Mailgun, Amazon SES), a deliverability-focused specialist (Postmark), and a new wave of developer-first challengers built around modern SDKs and AI-agent onboarding (Resend, Loops). Compare on documentation/DX quality, reliability and published SLAs, breadth of official SDKs and ecosystem integrations, and how quickly a developer or AI agent can self-serve a working API key. Pricing models cluster around per-volume tiers, with Amazon SES uniquely pure pay-as-you-go.
| API | Billed by | Free tier | Verified |
|---|---|---|---|
 SendGrid Transactional Email APIs | Per monthly email volume | Free tier or trial | Jun 27, 2026 |
 Resend Transactional Email APIs | Per monthly email volume | Free tier or trial | Jun 27, 2026 |
 Postmark Transactional Email APIs | Per monthly email volume | Free tier or trial | Jun 27, 2026 |
 Mailgun Transactional Email APIs | Per monthly email volume | Free tier or trial | Jun 27, 2026 |
 Amazon SES Transactional Email APIs | Pay-as-you-go per 1k emails | Free tier or trial | Jun 27, 2026 |
 Loops Transactional Email APIs | Contact-based plan (transactional included) | Free tier or trial | Jun 27, 2026 |
 SparkPost Transactional Email APIs | Volume tiers / custom enterprise | Free tier or trial | Jun 27, 2026 |