Mail Forwarder

A lightweight tool to forward emails from POP3/IMAP accounts to a specified SMTP destination written in Rust.

Gmail DOES NOT support POP3 or Gmailify for the forwarding email from third-party mail services, for more details, please refer to the official Gmail documentation. So, I wrote this tool to forward emails from POP3/IMAP accounts to a specified SMTP destination, which can be used with Gmail or any other email service that supports SMTP.

• Support for POP3 and IMAP protocols.
• Monitor multiple email accounts simultaneously.
• TLS/SSL support.
• Send notifications on successful forwarding via Telegram, file logging, or email.
• Configurable check intervals (in seconds).
• Save emails locally before deleting them from the source server, then retry forwarding before sending failure notifications.

You can also run the mail forwarder using the precompiled Docker image, which is available on GitHub Container Registry:

docker pull ghcr.io/mingcheng/mail-forwarder

The recommended Docker Compose configuration is:

services:
  mail-forwarder:
    image: ghcr.io/mingcheng/mail-forwarder
    network_mode: host
    environment:
      TZ: "Asia/Shanghai"
    volumes:
      - ./data:/app/
      - ./data/config.toml:/app/config.toml:ro # Mount the config file as read-only

Make sure you have Rust installed, then clone the repository and build the project:

cargo build --release

then run the binary if you have configured the config.toml file.

By default the application loads its configuration from /etc/mail-forwarder/config.toml. You can point it at any other location with the --config flag (see Usage). Create a config.toml file with the following content:

# Destination email address
forward_to = "target@example.com"

# Optional: local spool used to keep a copy before deleting from the source server.
local_mail_dir = "mail-forwarder-spool"
# Optional: number of SMTP forwarding attempts before failure notifications are sent.
forward_retry_attempts = 3

# Optional: Logging configuration
# log_level accepts the same syntax as the RUST_LOG environment variable
# (e.g. "info", "debug", "mail_forwarder=debug"). Defaults to "info".
log_level = "info"
# Optional: write logs to a file (in addition to stderr).
log_file = "mail-forwarder.log"
# Optional: when true, suppress stderr output (only the log file, if any, is written).
quiet = false

# Optional: Notifications when an email is successfully forwarded
[[notifications]]
type = "telegram"
chat_id = "your_telegram_chat_id"
token = "your_telegram_bot_token"

[[notifications]]
type = "file"
file_path = "forwarding_log.txt"

[[notifications]]
type = "email"
smtp_host = "smtp.gmail.com"
smtp_port = 587
smtp_username = "your_email@gmail.com"
smtp_password = "your_email_password"

# SMTP Sender Configuration (for sending forwarded emails)
[sender]
host = "smtp.gmail.com"
port = 587
username = "sender@gmail.com"
password = "app_password" 

# Receiver Example 1: POP3
[[receivers]]
protocol = "pop3"
host = "pop.gmail.com"
port = 995
username = "source1@gmail.com"
password = "app_password"
use_tls = true
check_interval_seconds = 60

# Receiver Example 2: IMAP
[[receivers]]
protocol = "imap"
host = "imap.outlook.com"
port = 993
username = "source2@outlook.com"
password = "app_password"
use_tls = true
imap_folder = "INBOX"
check_interval_seconds = 60

Note: For services like Gmail or Outlook, please use an App Password instead of your login password for security reasons. You can generate an App Password in your email account settings.

Note: Each fetched message is first written to local_mail_dir, then deleted from the source server, then forwarded. If all forwarding attempts fail, failure notifications are sent and the local .eml copy is retained for manual recovery. If source deletion fails, forwarding still continues and the local copy is kept as a recovery trail.

Run the binary:

./target/release/mail-forwarder

# Or with a specific config file
./target/release/mail-forwarder --config /path/to/config.toml

# Check configuration syntax, SMTP/POP3 account connectivity, and send test notifications
./target/release/mail-forwarder --config /path/to/config.toml --check

Account and notification checks time out after 30 seconds each, so one slow server will not block the entire check indefinitely. If notification handlers are configured, --check sends a test notification through each one.

This project is licensed under the MIT License. See the LICENSE file for details.