What to Look for in a Developer Email API

Choosing an email API shouldn't take days of research. Here's what actually matters when you're evaluating options for transactional email.

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1. Authentication & Deliverability

This is non-negotiable. If your emails land in spam, nothing else matters.

What to check:

Red flags:

• No guidance on DNS setup
• No way to verify authentication status
• No automatic suppression of bounced addresses

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2. Speed & Reliability

Transactional emails are time-sensitive. A password reset that takes 30 seconds to arrive feels broken.

What to check:

Questions to ask:

• What's the p95 delivery time?
• Do you queue emails or send immediately?
• What happens during an outage—do emails queue or fail?

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3. Developer Experience

You'll integrate once, then forget about it. But that integration shouldn't take a week.

What to check:

Code should be simple:

// Good: minimal boilerplate
await email.send({
  from: 'hello@myapp.com',
  to: 'user@example.com',
  subject: 'Welcome!',
  html: '<h1>Hello</h1>'
})

// Bad: excessive configuration
const client = new EmailClient({
  apiKey: process.env.KEY,
  region: 'us-east-1',
  timeout: 30000,
  retryPolicy: { maxRetries: 3, backoff: 'exponential' },
  // ... 20 more options
})

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4. Webhook Events

You need to know when emails bounce, get marked as spam, or fail to deliver.

Essential events:

Nice to have:

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5. Templates (Optional)

Some APIs let you store templates server-side with variable substitution.

Benefits:

• Non-developers can edit email content
• Consistent branding across emails
• Less code to maintain

Trade-offs:

• Another system to manage
• Version control is harder
• Template syntax varies by provider

Alternative:

Build emails in code with React Email or similar. Full type safety, version controlled, testable.

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6. Pricing Model

Email API pricing falls into two camps:

Bundled plans

Fixed monthly fee for X emails + Y domains.

Pros: Predictable costs, often includes generous limits Cons: Pay for capacity you might not use

Best for: High-volume senders, single-product companies

Usage-based

Pay per email and/or per domain.

Pros: Costs scale with actual usage Cons: Less predictable at scale

Best for: Multi-project developers, agencies, early-stage products

What to check:

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7. Dashboard & Logs

You don't need fancy analytics. You need to debug issues.

Must-haves:

• Email logs with status (delivered, bounced, etc.)
• Search by recipient or message ID
• Raw event timeline per email
• Domain verification status

Nice-to-haves:

• Aggregate stats (volume, bounce rate)
• Visual charts
• Export functionality

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Quick Evaluation Checklist

Use this when comparing options:

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What Usually Doesn't Matter

For transactional email specifically:

• Open tracking — Privacy concerns, not actionable for transactional
• Click tracking — Same as above
• A/B testing — That's for marketing campaigns
• Complex segmentation — You're sending to one person at a time
• Drag-and-drop editor — Code your templates or use React Email

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Bottom Line

Pick an API that:

1. Handles authentication properly (deliverability is everything)
2. Has an SDK you like using (you'll integrate once)
3. Gives you webhook events (bounce/complaint handling is mandatory)
4. Prices fairly for your usage pattern

Everything else is nice-to-have.

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Next Steps

• Check our email deliverability checklist for post-integration setup
• Learn about DKIM, SPF, and DMARC if you're new to email authentication
• See our framework guides for integration examples