principlejavascriptMajor
SMTP vs Email API: choosing SendGrid or Resend for transactional email
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sendgridresendemail apiesptransactional emailsmtp vs apiemail deliverability
Problem
Choosing between raw SMTP and an email API (SendGrid, Resend, Postmark) is not obvious. SMTP feels simpler but lacks analytics, bounce handling, and deliverability infrastructure. Email APIs add a dependency but provide critical production features.
Solution
Use an Email Service Provider (ESP) API like Resend, SendGrid, or Postmark for production transactional email. They provide managed deliverability, bounce/complaint webhooks, click/open tracking, and instant API keys. Use SMTP only when required by specific tooling or legacy constraints.
Why
Deliverability from a shared or self-hosted SMTP server is poor without an established IP reputation. ESPs maintain warm IPs with major inbox providers, dramatically improving inbox rates. Their APIs are also simpler to use than raw SMTP.
Gotchas
- Resend is developer-focused with a clean SDK; SendGrid is more feature-heavy and enterprise-oriented
- ESP pricing is based on email volume — factor cost into architecture decisions at scale
- Always verify your sending domain with SPF and DKIM records in your DNS regardless of which ESP you use
- Store your API key in environment variables, never in source code
Code Snippets
Send email with Resend SDK
import { Resend } from 'resend';
const resend = new Resend(process.env.RESEND_API_KEY);
const { data, error } = await resend.emails.send({
from: 'Brand <no-reply@yourdomain.com>',
to: ['user@example.com'],
subject: 'Welcome!',
html: '<p>Welcome to our platform!</p>',
});
if (error) console.error('Email send failed:', error);Context
Choosing an email sending strategy for production applications
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