The best API for sending welcome emails in Node.js depends on one practical question: is email the product, or is it the first backend capability? For an edtech contact form, I would keep queue routing in the application, use a reusable welcome template, and choose the provider whose next integration will cost the fewest engineering hours. A focused email service wins the smallest job. A broader REST surface wins when the roadmap needs more backend capabilities behind one contract.

Option Integration style Best fit Main boundary

Resend Focused email API A small transactional-mail workflow Less useful when email is one part of a wider backend

SendGrid Email platform and API Teams with established email operations More configuration than a solo product may need

Mailgun Email API with delivery operations Teams centered on domains and delivery Still a mail-specific integration

Infrai One REST contract across backend modules A roadmap that values one discovery surface No webhooks, SMTP relay, or hosted email…