How It Works

MailLighter is built on Office.js, Microsoft’s official API for Outlook add-ins. This page explains the technical architecture and how your emails are processed.

Architecture Overview

┌─────────────────────────────────────────┐
│              Outlook Desktop            │
│  ┌───────────────────────────────────┐  │
│  │         MailLighter Add-in        │  │
│  │  ┌─────────┐  ┌───────────────┐  │  │
│  │  │ Commands │  │   Office.js   │  │  │
│  │  │ (JS/ES6) │  │     API       │  │  │
│  │  └────┬─────┘  └───────┬───────┘  │  │
│  │       │   Read/Write    │          │  │
│  │       └────────┬────────┘          │  │
│  └────────────────┼──────────────────┘  │
│                   ▼                     │
│            Email Content                │
│         (stays in Outlook)              │
└─────────────────────────────────────────┘
          No external server

Processing Flow

When you run a MailLighter command:

1. Outlook triggers the command via its ribbon dropdown menu
2. Office.js reads the email body using the ReadWriteItem permission
3. MailLighter processes the HTML entirely in JavaScript on your device
4. The cleaned content is written back to the email draft via Office.js

The entire operation happens locally within Outlook. No data is sent to any external server at any point.

Technology Stack

Component	Technology
Runtime	Office.js (via Outlook)
Language	JavaScript (ES6+)
Transpiler	Babel
Bundler	webpack 5
UI	HTML / CSS (minimal)
Localization	Custom i18n module (EN, FR, ES)

Permission Model

MailLighter requests a single permission: ReadWriteItem.

This is the minimum permission required to:

• Read the email body (to process it)
• Write the cleaned email body back

MailLighter does not request:

• ReadWriteMailbox (full mailbox access)
• ReadItem without write (would prevent cleaning)
• Any network-related permission

Localization

MailLighter is available in 3 languages:

• English (default)
• French
• Spanish

The language is automatically detected from your Outlook settings. All command labels, descriptions, and tooltips are translated.

Open Source

The full source code is available on GitHub under the MIT license. You can audit the code, contribute, or fork it.