Email Bot: Email to Discord Forwarder

A Rust application that monitors multiple email accounts and forwards new messages to Discord channels via webhooks. Supports IMAP (Gmail, custom servers) and Microsoft Graph API (Outlook/Hotmail).

Features

• IMAP with IDLE — push-based, real-time email notifications (Gmail, custom servers)
• Microsoft Graph API — REST polling for Outlook/Hotmail accounts
• Multi-mailbox — monitor all mailboxes or specific ones per account
• OAuth2 Device Code Flow — for Microsoft accounts (no browser needed on server)
• Local state tracking — prevents duplicate forwarding across restarts
• Exponential backoff — automatic reconnection on failures
• Discord rate limit handling — retries with respect to Discord's rate limits
• Graceful shutdown — clean Ctrl+C handling

Setup

Prerequisites

• Rust 1.85+ (edition 2024)
• A Discord webhook URL
• Email account credentials (IMAP password or OAuth2)

Discord Webhook

1. Open your Discord server
2. Go to Channel Settings → Integrations → Webhooks
3. Click New Webhook, copy the URL

Gmail (IMAP)

Gmail requires an App Password:

1. Enable 2-Factor Authentication on your Google account
2. Go to App Passwords
3. Generate a password for "Mail"

Any IMAP server should work with this app.

Outlook / Hotmail (Graph API)

Microsoft personal accounts require OAuth2 via Graph API:

1. Go to Azure Portal → App registrations
2. Click New registration
   • Name: Email Bot
   • Supported account types: Personal Microsoft accounts only
   • Redirect URI: leave blank
3. Copy the Application (client) ID
4. Go to API permissions → Add a permission → Microsoft Graph → Delegated
   • Add Mail.ReadWrite
   • Click Grant admin consent
5. Go to Authentication → Advanced settings
   • Set Allow public client flows to Yes
   • Click Save

Configuration

cp config.example.json config.json

Gmail (IMAP) Account

{
  "name": "Personal Gmail",
  "protocol": "imap",
  "imap_server": "imap.gmail.com",
  "imap_port": 993,
  "username": "you@gmail.com",
  "password": "your-app-password",
  "mailboxes": ["*"],
  "discord_webhook_url": "https://discord.com/api/webhooks/..."
}

Outlook / Hotmail (Graph) Account

{
  "name": "Personal Hotmail",
  "protocol": "graph",
  "auth_method": "oauth2",
  "client_id": "YOUR_AZURE_CLIENT_ID",
  "username": "you@hotmail.com",
  "discord_webhook_url": "https://discord.com/api/webhooks/..."
}

Configuration Fields

Field	Required	Default	Description
name	✅	—	Display name for the account
protocol	—	"imap"	"imap" or "graph"
imap_server	IMAP only	—	IMAP server hostname
imap_port	—	993	IMAP server port
username	✅	—	Email address
password	IMAP password auth	—	IMAP password or app password
auth_method	—	"password"	"password" or "oauth2"
client_id	OAuth2/Graph	—	Azure AD Application (client) ID
oauth2_scope	—	Mail.ReadWrite	OAuth2 scope (override if needed)
mailboxes	—	["INBOX"]	Mailboxes to monitor. ["*"] = all
discord_webhook_url	✅	—	Discord webhook URL

Running

# Build and run
cargo run

# Custom config path
cargo run -- /path/to/config.json

# Debug logging
RUST_LOG=debug cargo run

On first run with an OAuth2 account, you'll see a device code prompt:

╔══════════════════════════════════════════════════════════╗
║           OAuth2 Authentication Required                ║
║  1. Open: https://www.microsoft.com/link                 ║
║  2. Enter code: ABCD1234                                 ║
║  Waiting for authorization...                            ║
╚══════════════════════════════════════════════════════════╝

Open the URL in any browser, enter the code, and authorize. Tokens are saved to tokens.json and refreshed automatically.

Production Deployment with systemd

1. Build Release Binary

cargo build --release

2. Set Up Directory

sudo mkdir -p /opt/email-bot
sudo cp target/release/email-bot /opt/email-bot/
sudo cp config.json /opt/email-bot/

3. Create System User

sudo useradd --system --no-create-home --shell /usr/sbin/nologin email-bot
sudo chown -R email-bot:email-bot /opt/email-bot
sudo chmod 600 /opt/email-bot/config.json

4. Create systemd Service

sudo tee /etc/systemd/system/email-bot.service << 'EOF'
[Unit]
Description=Email to Discord Forwarder
After=network-online.target
Wants=network-online.target

[Service]
Type=simple
User=email-bot
Group=email-bot
WorkingDirectory=/opt/email-bot
ExecStart=/opt/email-bot/email-bot
Restart=always
RestartSec=10

# Logging
Environment=RUST_LOG=info
StandardOutput=journal
StandardError=journal
SyslogIdentifier=email-bot

# Security hardening
NoNewPrivileges=true
ProtectSystem=strict
ProtectHome=true
ReadWritePaths=/opt/email-bot
PrivateTmp=true
ProtectKernelTunables=true
ProtectKernelModules=true
ProtectControlGroups=true

[Install]
WantedBy=multi-user.target
EOF

5. Enable and Start

sudo systemctl daemon-reload
sudo systemctl enable email-bot
sudo systemctl start email-bot

6. Manage the Service

# Check status
sudo systemctl status email-bot

# View logs
sudo journalctl -u email-bot -f

# Restart after config changes
sudo systemctl restart email-bot

# Stop
sudo systemctl stop email-bot

Note: If using OAuth2 (Graph), you must run email-bot interactively the first time to complete the device code authorization. After tokens.json is created, the service can run unattended with automatic token refresh.

Files

File	Description	Git-tracked
config.json	Account credentials & settings	❌
config.example.json	Template configuration	✅
state.json	Forwarded message IDs (auto-created)	❌
tokens.json	OAuth2 tokens (auto-created)	❌

Security

⚠️ config.json, state.json, and tokens.json contain secrets and are gitignored.

Never commit them to version control. Use config.example.json as a template.

License

MIT