Architecture Overview

NexoMailer is a Headless SDK designed for deep integration into your existing Node.js ecosystem. It removes the need for a third-party dashboard, giving you complete control over your data and infrastructure.

High-Level Architecture

NexoMailer follows a modular design where each package handles a specific part of the email lifecycle.

The Core Components

1. The Headless Engine (core)

The brain of the system. It manages configuration, initializes plugins, and orchestrates the failover between different email providers.

2. Persistence Layer (analytics)

Unlike traditional mailers, NexoMailer has a built-in memory. It connects directly to your MongoDB to store message history, status, and tracking events. You own the database; we just provide the schema and logic.

3. Instrumentation & Tracking (tracking)

This module rewrites your email HTML to include tracking pixels and redirected links. It includes a mountable Express middleware that captures events and sends them to the Analytics layer.

The Data Flow (Email Lifecycle)

1. Generation: Your app calls mailer.send().
2. Augmentation: The templates and ai modules generate the responsive HTML.
3. Instrumentation: The tracking module injects a unique Nexo ID into the links.
4. Dispatch: The providers module sends the email via the primary or backup service.
5. Collection: When a user opens the email, your backend (via our middleware) captures the event.
6. Sync: The status in your MongoDB is automatically updated from SENT to OPENED.

Why Headless?

• Zero Vendor Lock-in: You can switch email providers in seconds.
• Privacy by Design: Your recipient list and email content never leave your infrastructure.
• Customization: Build the exact dashboard your team needs using our Analytics API.

[!TIP] Since NexoMailer is headless, you can integrate it into any existing Node.js backend (Express, NestJS, Fastify, etc.) with just a few lines of code.