Mock Resend

A mock server implementation of the Resend API, useful for testing and development without using the live Resend service.

Features

• API Compatibility: Full REST API compatible with Resend's endpoints
• Email Management: Send, list, track, and cancel emails
• Domain Management: Configure and verify sending domains
• API Keys: Create and manage API keys with granular permissions
• Webhooks: Configure webhooks with delivery tracking and retry logic
• Audiences & Contacts: Manage email lists and subscribers
• Web UI: Optional dashboard for visual management
• Persistence: SQLite database with JSON backup
• Docker Support: Production-ready containerized deployment

Quick Start

Prerequisites

• Rust 1.70+
• Cargo
• (Optional) Docker & Docker Compose

Running Locally

# Clone the repository
git clone https://github.com/hongkongkiwi/mock-resend.git
cd mock-resend

# Run with default settings
cargo run

# Server starts at http://localhost:3030

Running with Web UI

cargo run --features web-ui -- --web

Access the web UI at http://localhost:3030

Using Docker

# Build and start
docker-compose up -d

# View logs
docker-compose logs -f

# Stop
docker-compose down

Configuration

Edit config.yaml to customize settings:

server:
  host: "0.0.0.0"
  port: 3030

cors:
  allow_origin: ["*"]
  allow_methods: ["*"]
  allow_headers: ["*"]

rate_limit:
  window_seconds: 60
  default_max: 1000

database:
  url: "sqlite:./data/mock-resend.db"
  max_connections: 10
  min_connections: 1

persistence:
  enabled: true
  file_path: "./data/store.json"
  save_interval_seconds: 30

logging:
  level: "info"

web_auth:
  enabled: false

Command Line Options

mock-resend [OPTIONS]

Options:
  -c, --config <PATH>  Path to config file (default: "config.yaml")
  -w, --web           Enable web UI
  -p, --port <PORT>   Port (overrides config)
  -h, --host <HOST>   Host (overrides config)

API Reference

Base URL

http://localhost:3030

Authentication

Most endpoints require a Bearer token:

curl -H "Authorization: Bearer re_test_123" http://localhost:3030/v1/emails

API keys follow the format re_<env>_<type>_<random>_<secret>.

Endpoints

Health & Documentation

Method	Endpoint	Description
GET	/health	Health check
GET	/docs	Swagger UI redirect
GET	/docs/openapi.json	OpenAPI specification

Account

Method	Endpoint	Description
GET	/v1/account	Get account information

Emails

Method	Endpoint	Description
POST	/v1/emails	Send an email
GET	/v1/emails	List all emails
GET	/v1/emails/:id	Get email details
PATCH	/v1/emails/:id	Update email
POST	/v1/emails/:id/cancel	Cancel pending email
POST	/v1/batch	Send batch emails

Example: Send an email

curl -X POST http://localhost:3030/v1/emails \
  -H "Authorization: Bearer re_test_123" \
  -H "Content-Type: application/json" \
  -d '{
    "from": "onboarding@resend.dev",
    "to": ["user@example.com"],
    "subject": "Hello World",
    "html": "<p>Welcome!</p>"
  }'

API Keys

Method	Endpoint	Description
GET	/v1/api-keys	List API keys
POST	/v1/api-keys	Create API key
DELETE	/v1/api-keys/:id	Delete API key
POST	/v1/api-keys/verify	Verify API key

Domains

Method	Endpoint	Description
GET	/v1/domains	List domains
POST	/v1/domains	Create domain
GET	/v1/domains/:id	Get domain details
DELETE	/v1/domains/:id	Delete domain
GET	/v1/domains/:id/records	Get DNS records
POST	/v1/domains/:id/verify	Verify domain

Audiences & Contacts

Method	Endpoint	Description
GET	/v1/audiences	List audiences
POST	/v1/audiences	Create audience
GET	/v1/audiences/:id	Get audience
DELETE	/v1/audiences/:id	Delete audience
GET	/v1/audiences/:id/members	List audience members
POST	/v1/audiences/:id/members	Add audience member
GET	/v1/contacts	List contacts
POST	/v1/contacts	Create contact

Webhooks

Method	Endpoint	Description
GET	/v1/webhooks	List webhook configs
POST	/v1/webhooks	Create webhook
GET	/v1/webhooks/:id	Get webhook
PATCH	/v1/webhooks/:id	Update webhook
DELETE	/v1/webhooks/:id	Delete webhook
GET	/v1/webhook-deliveries	List deliveries
POST	/v1/webhook-deliveries/:id/retry	Retry delivery
POST	/v1/webhooks/simulate	Simulate webhook event

Webhook Event Types:

• email.sent
• email.delivered
• email.bounced
• email.complained
• email.opened
• email.clicked

Statistics

Method	Endpoint	Description
GET	/v1/stats	Get sending statistics

Internal

Method	Endpoint	Description
POST	/_internal/reset	Reset all data

Web UI

The optional web UI provides a visual interface for managing your mock Resend instance.

Available Pages

Route	Description
/	Dashboard with stats overview
/emails	View and send emails
/domains	Manage domains
/api-keys	Manage API keys
/webhooks	Configure and monitor webhooks
/audiences	Manage audience lists

Components

The UI includes reusable components:

• Sidebar - Navigation menu
• Header - Page headers with actions
• Card - Content containers
• Table - Sortable data tables
• Modal - Dialog forms
• ToastContainer - Notifications

Building for Production

# Build with web UI
cargo leptos build --features web-ui

Project Structure

mock-resend/
├── Cargo.toml              # Rust dependencies
├── config.yaml             # Configuration file
├── Dockerfile              # Container definition
├── docker-compose.yml      # Docker services
├── leptos.toml             # Leptos configuration
│
├── src/
│   ├── main.rs             # Entry point
│   ├── models.rs           # Data models
│   ├── middleware.rs       # Auth & rate limiting
│   ├── persistence.rs      # JSON file persistence
│   ├── openapi.rs          # OpenAPI specification
│   │
│   ├── db/
│   │   ├── mod.rs          # Database setup
│   │   └── entities/       # SQLx entities
│   │       ├── email.rs
│   │       ├── domain.rs
│   │       ├── api_key.rs
│   │       ├── webhook_config.rs
│   │       └── ...
│   │
│   ├── routes/
│   │   ├── mod.rs          # Route definitions
│   │   ├── emails.rs       # Email endpoints
│   │   ├── domains.rs      # Domain endpoints
│   │   ├── webhooks.rs     # Webhook endpoints
│   │   ├── account.rs      # Account endpoints
│   │   └── web_ui.rs       # Web UI routes
│   │
│   └── web/                # Web UI (optional)
│       ├── app.rs
│       ├── auth.rs
│       ├── components/
│       │   ├── button.rs
│       │   ├── card.rs
│       │   ├── modal.rs
│       │   ├── table.rs
│       │   └── ...
│       └── pages/
│           ├── dashboard.rs
│           ├── emails.rs
│           ├── domains.rs
│           └── ...
│
├── data/                   # Data storage
│   └── store.json          # JSON backup
│
└── tests/
    └── integration_test.rs # Integration tests

Development

Running Tests

# Run all tests
cargo test

# Run with verbose output
cargo test -- --nocapture

Adding New Endpoints

1. Define models in src/models.rs
2. Create database entities in src/db/entities/
3. Add route handlers in appropriate src/routes/*.rs
4. Register route in src/routes/mod.rs
5. Update OpenAPI spec in src/openapi.rs

Database Migrations

# Run migrations
cargo run --migrate

Persistence

The application supports two persistence mechanisms:

1. SQLite Database - Primary storage using SQLx
2. JSON Backup - Automatic periodic backup to data/store.json

Both are kept in sync automatically.

Deployment

Docker

# Build image
docker build -t mock-resend .

# Run container
docker run -p 3030:3030 \
  -v $(pwd)/data:/data \
  -v $(pwd)/config.yaml:/data/config.yaml:ro \
  mock-resend

Environment Variables

Variable	Description
RUST_LOG	Logging level (info, debug, warn, error)
DATABASE_URL	Override database connection string

Troubleshooting

Port Already in Use

# Find process using port 3030
lsof -i :3030

# Kill the process
kill <PID>

Database Locked

If using SQLite, ensure no other processes are accessing the database file.

Web UI Not Loading

Ensure you built with the web-ui feature:

cargo run --features web-ui -- --web

License

MIT License - see LICENSE file for details.

Contributing

1. Fork the repository
2. Create a feature branch
3. Make your changes
4. Run tests: cargo test
5. Submit a pull request

Credits

Mock Resend is not affiliated with, endorsed by, or sponsored by Resend Inc. This project provides a mock implementation for testing purposes.