Email is still the backbone of internet communication — transactional emails (password resets, confirmations, receipts) and marketing emails (newsletters, onboarding, drip campaigns) power most web apps. Choosing the right email API affects deliverability, developer experience, and cost per thousand emails. This comparison covers the leading email services for developers.
Quick Comparison
| Feature | Resend | SendGrid (Twilio) | Postmark | Amazon SES |
|---|---|---|---|---|
| Type | Modern email API for developers | Transactional + marketing email | Transactional email only | Bare-metal email sending |
| Free Tier | 100 emails/day | 100 emails/day | 100 emails (total, not /day) | 62,000 emails/month (from EC2) |
| Cost (per 1,000) | $0.13-$0.33 | $0.12-$0.20 | $0.45 (flat) | $0.10 |
| Deliverability | Excellent (modern infrastructure) | Good (large shared IP pools) | Excellent (fastest delivery) | Good (requires configuration) |
| Setup Complexity | Very Low (minimal DNS setup) | Medium (SPF, DKIM, DMARC) | Low (guided DNS setup) | High (domain verification, SPF, DKIM, custom MAIL FROM, suppression lists) |
| SDK / API Quality | Excellent (modern REST, Node/Python/Go/Ruby SDKs) | Good (REST API, legacy SMTP) | Excellent (clean REST API) | Basic (REST API, raw SMTP) |
| React Email Support | Yes (first-class, built by same team) | No (HTML templates) | No (HTML + templates) | No (raw email) |
| Email Builder / Templates | React Email (code-based) | Dynamic Templates (WYSIWYG + code) | Templates (code-based) | None (send raw HTML) |
| Analytics / Tracking | Opens, clicks, bounces, complaints | Opens, clicks, bounces, unsubscribe | Opens, clicks, bounces, spam score | Opens, clicks (via SNS + custom code) |
| Best For | Modern dev stack, React Email users | Marketing + transactional combined | Transactional email, fast delivery | High volume, lowest cost |
When to Choose Each Service
Resend — Best for: Modern JavaScript/TypeScript stacks. Resend is the newest entrant with the best developer experience — built by the React Email team, first-class React Email support, and a clean API. Weak spot: Newer (fewer production track records); free tier is limited (100/day).
SendGrid — Best for: Teams that need both transactional and marketing email in one platform. SendGrid's template builder and marketing automation are the main differentiators. Weak spot: Deliverability can be inconsistent on shared IPs; acquired by Twilio, focus has shifted.
Postmark — Best for: Transactional email where speed and deliverability are critical. Postmark is famously fast (most emails delivered in <5 seconds) and has excellent deliverability. Weak spot: No marketing email features; more expensive per email ($0.45/1K).
Amazon SES — Best for: High-volume sending where cost is the primary concern. SES is 10x cheaper than competitors — $0.10 per 1,000 emails. Weak spot: Steep setup (domain verification, SPF, DKIM, DMARC, suppression lists all manual); no templates; raw API.
Decision Matrix
| Scenario | Best Service | Why |
|---|---|---|
| Modern JS/TS project, want best DX | Resend | Best API design, React Email integration |
| Marketing + transactional combined | SendGrid | Templates + marketing automation built in |
| Transactional only, need fast reliable delivery | Postmark | Fastest delivery, best deliverability |
| High volume (>100K/month), cost matters | Amazon SES | 10x cheaper, reliable at scale |
| Newsletter or marketing automation | SendGrid or dedicated ESP | SendGrid for simplicity, dedicated ESP for advanced |
Bottom line: Resend is the best default for new projects — modern API, React Email support, and great DX. Postmark wins when deliverability is the #1 priority. SES is the cost leader for high volume. SendGrid bridges transactional and marketing — useful if you need both but don't want two vendors. See also: Best Log Management Tools and Webhook Implementation Guide.