@workermailer/smtp

SMTP docs

Overview

What the SMTP package does, when to use it, and what ships today.

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v0.1.4 Release notes

SMTP overview

@workermailer/smtp is the Worker Mailer package for direct SMTP delivery from Cloudflare Workers. It uses Cloudflare TCP sockets instead of a separate Node mail relay, so the same Worker that handles your request can also talk to the SMTP server.

Why this package exists

Traditional SMTP libraries expect a long-lived Node.js runtime and access to platform sockets that do not map cleanly to Cloudflare Workers. This package keeps the API small and Worker-native while still covering the parts teams actually need in production.

What ships today

  • Direct SMTP connections from Cloudflare Workers using cloudflare:sockets
  • TypeScript-first transport and message types
  • Plain text and HTML bodies
  • Attachments and CID inline images
  • DSN configuration for delivery notifications
  • Lifecycle hooks for connection, success, failure, and close
  • Queue helpers for Cloudflare Queues
  • EmDash sandbox bundle in emdash-plugin/

When to choose SMTP

Choose SMTP when you:

  • already have a provider or mailbox service that exposes SMTP credentials
  • need DSN knobs or lower-level transport control
  • want to keep the same message model across Worker-first infrastructure

Choose @workermailer/resend when your team prefers the Resend HTTP API and a lighter operational model.

Package shape

The package exposes two main entry points:

  • @workermailer/smtp: the mailer, types, error classes, and utilities
  • @workermailer/smtp/queue: helpers for enqueuing and processing queued sends

Production notes

  • Use Cloudflare Workers compatibility flags that enable Node compatibility.
  • Keep credentials in Worker secrets or your deployment platform secret store.
  • Prefer queue-based delivery for workflows that should not block user-facing responses.

Where to go next