Nodemailer

Nodemailer is the standard library for sending emails from Node.js. It's been the standard for sending email in Node.js for over a decade.

Completely free under a permissive license. You get SMTP support, OAuth2 authentication, HTML and plain text emails, attachments, embedded images, DKIM signing, and connection pooling. It works with any SMTP server: Gmail, SendGrid, Mailgun, Amazon SES, your own Postfix server, whatever.

No paid tier, no hosted service. It's a library. You install it, configure your SMTP credentials, and send emails. Everyone building Node.js apps that send email: use Nodemailer as your transport layer. Pair it with an ESP (email service provider) for deliverability. If you're sending marketing emails or newsletters, use a dedicated platform instead.

The catch: Nodemailer sends emails. That's it. It doesn't manage email templates, track opens/clicks, handle unsubscribes, or give you analytics. For those, you need a service like Resend, SendGrid, or Mailgun on top. Also, sending emails reliably at scale (deliverability, reputation management, bounce handling) is a whole discipline that Nodemailer doesn't solve. It just sends.