Lightweight SMTP relay using msmtpd as a Docker image.

• Features
• Build locally
• Image
• Environment variables
• Ports
• Usage
  • Docker Compose
  • Kubernetes
  • Command line
• Upgrade
• Contributing
• License

• Run as non-root user
• Latest msmtp/msmtpd release compiled from source
• Bind to unprivileged port
• Multi-platform image

git clone https://github.com/crazy-max/docker-msmtpd.git
cd docker-msmtpd

# Build image and output to docker (default)
docker buildx bake

# Build multi-platform image
docker buildx bake image-all

Following platforms for this image are available:

$ docker buildx imagetools inspect crazymax/msmtpd --format "{{json .Manifest}}" | \
  jq -r '.manifests[] | select(.platform.os != null and .platform.os != "unknown") | .platform | "\(.os)/\(.architecture)\(if .variant then "/" + .variant else "" end)"'

linux/386
linux/amd64
linux/arm/v6
linux/arm/v7
linux/arm64
linux/ppc64le
linux/s390x

• TZ: Timezone assigned to the container (default UTC)
• PUID: Daemon user id (default 1500)
• PGID: Daemon group id (default 1500)
• SMTP_HOST: SMTP relay server to send the mail to. required
• SMTP_PORT: Port that the SMTP relay server listens on. Default 25 or 465 if TLS.
• SMTP_TLS: Enable or disable TLS (also known as SSL) for secured connections (on or off).
• SMTP_STARTTLS: Start TLS from within the session (on, default), or tunnel the session through TLS (off).
• SMTP_TLS_CHECKCERT: Enable or disable checks of the server certificate (on or off). They are enabled by default.
• SMTP_AUTH: Enable or disable authentication and optionally choose a method to use. The argument on chooses a method automatically.
• SMTP_USER: Set the username for authentication. Authentication must be activated with the SMTP_AUTH env var.
• SMTP_PASSWORD: Set the password for authentication. Authentication must be activated with the SMTP_AUTH env var.
• SMTP_DOMAIN: Argument of the SMTP EHLO command (default localhost)
• SMTP_FROM: Set the envelope-from address. Supported substitution patterns can be found here.
• SMTP_ALLOW_FROM_OVERRIDE: Allow configured envelope-from address to be overriden by actual SMTP MAIL FROM . Can be on or off (default on)
• SMTP_SET_FROM_HEADER: When to set a From header. Can be auto, on or off (default auto)
• SMTP_SET_DATE_HEADER: When to set a Date header. Can be auto or off (default auto)
• SMTP_REMOVE_BCC_HEADERS: Controls whether to remove Bcc headers. Can be on or off (default on)
• SMTP_UNDISCLOSED_RECIPIENTS: When set, the original To, Cc, and Bcc headers of the mail are removed and a single new header line To: undisclosed-recipients:; is added. Can be on or off (default off)
• SMTP_DSN_NOTIFY: Set the condition(s) under which the mail system should send DSN (Delivery Status Notification) messages as comma separated values. Available values are off, never, failure, delay and success (default off)
• SMTP_DSN_RETURN: Controls how much of a mail should be returned in DSN (Delivery Status Notification) messages. Can be headers, full or off (default off)

• 2500: SMTP relay port

Docker compose is the recommended way to run this image. You can use the following docker compose template, then run the container:

docker compose up -d
docker compose logs -f

To install on a Kubernetes cluster, you can use the following kubernetes deployment template, then create the deployment:

kubectl apply -f deployment.yaml

You can also use the following minimal command:

$ docker run -d -p 2500:2500 --name msmtpd \
  -e "SMTP_HOST=smtp.example.com" \
  crazymax/msmtpd

Recreate the container whenever I push an update:

docker compose pull
docker compose up -d

Want to contribute? Awesome! The most basic way to show your support is to star the project, or to raise issues. You can also support this project by becoming a sponsor on GitHub or by making a PayPal donation to ensure this journey continues indefinitely!

Thanks again for your support, it is much appreciated! 🙏

MIT. See LICENSE for more details.