postfix-docker 📮🐳

Docker Image

Creates a Docker container with an installation of the postfix MTA. Additionally it has an IMAP server (dovecot) for accessing the archives of sent email. All email is BCC'd to the mailarchive account.

Running

Running with Docker

To run the cisagov/postfix image via Docker:

docker run cisagov/postfix:0.0.4

Running with Docker Compose

1. Create a docker-compose.yml file similar to the one below to use Docker Compose or use the sample docker-compose.yml provided with this repository.

   ---
   version: "3.7"
   
   services:
     postfix:
       build:
         # VERSION must be specified on the command line:
         # e.g., --build-arg VERSION=0.0.4
         context: .
         dockerfile: Dockerfile
       image: cisagov/postfix
       init: true
       restart: always
       environment:
         - PRIMARY_DOMAIN=example.com
         - RELAY_IP=172.16.202.1/32
       networks:
         front:
           ipv4_address: 172.16.202.2
       ports:
         - target: "25"
           published: "1025"
           protocol: tcp
           mode: host
         - target: "587"
           published: "1587"
           protocol: tcp
           mode: host
         - target: "993"
           published: "1993"
           protocol: tcp
           mode: host
   
   networks:
     front:
       driver: bridge
       ipam:
         driver: default
         config:
           - subnet: 172.16.202.0/24

2. Start the container and detach:

   docker compose up --detach

Using secrets with your container

This container also supports passing sensitive values via Docker secrets. Passing sensitive values like your credentials can be more secure using secrets than using environment variables. See the secrets section below for a table of all supported secret files.

1. To use secrets, populate the following files in the src/secrets directory:

• fullchain.pem
• privkey.pem
• users.txt

1. Then add the secrets to your docker-compose.yml file:

   ---
   version: "3.7"
   
   secrets:
     fullchain_pem:
       file: ./src/secrets/fullchain.pem
     privkey_pem:
       file: ./src/secrets/privkey.pem
     users_txt:
       file: ./src/secrets/users.txt
   
   services:
     postfix:
       build:
         # VERSION must be specified on the command line:
         # e.g., --build-arg VERSION=0.0.4
         context: .
         dockerfile: Dockerfile
       image: cisagov/postfix
       init: true
       restart: always
       environment:
         - PRIMARY_DOMAIN=example.com
         - RELAY_IP=172.16.202.1/32
       networks:
         front:
           ipv4_address: 172.16.202.2
       ports:
         - target: "25"
           published: "1025"
           protocol: tcp
           mode: host
         - target: "587"
           published: "1587"
           protocol: tcp
           mode: host
         - target: "993"
           published: "1993"
           protocol: tcp
           mode: host
       secrets:
         - source: fullchain_pem
           target: fullchain.pem
         - source: privkey_pem
           target: privkey.pem
         - source: users_txt
           target: users.txt
   
   networks:
     front:
       driver: bridge
       ipam:
         driver: default
         config:
           - subnet: 172.16.202.0/24

Updating your container

Docker Compose

1. Pull the new image from Docker Hub:

   docker compose pull

2. Recreate the running container by following the previous instructions:

   docker compose up --detach

Docker

1. Stop the running container:

   docker stop <container_id>

2. Pull the new image:

   docker pull cisagov/postfix:0.0.4

3. Recreate and run the container by following the previous instructions.

Image tags

The images of this container are tagged with semantic versions of the underlying Postfix project that they containerize. It is recommended that most users use a version tag (e.g. :0.0.4).

Image:tag	Description
cisagov/postfix:0.0.4	An exact release version.
cisagov/postfix:0.0	The most recent release matching the major and minor version numbers.
cisagov/postfix:0	The most recent release matching the major version number.
cisagov/postfix:edge	The most recent image built from a merge into the develop branch of this repository.
cisagov/postfix:nightly	A nightly build of the develop branch of this repository.
cisagov/postfix:latest	The most recent release image pushed to a container registry. Pulling an image using the :latest tag should be avoided.

See the tags tab on Docker Hub for a list of all the supported tags.

Volumes

Mount point	Purpose
/var/log	System logs
/var/spool/postfix	Mail queues

Ports

The following ports are exposed by this container:

Port	Purpose
25	SMTP relay
587	Mail submission
993	IMAPS

The sample Docker composition publishes the exposed ports at 1025, 1587, and 1993, respectively.

Environment variables

Required

Name	Purpose
PRIMARY_DOMAIN	The primary domain of the mail server.

Optional

Name	Purpose	Default
RELAY_IP	An IP address that is allowed to relay mail without authentication.	null

Secrets

Filename	Purpose
fullchain.pem	Public key for the Postfix server.
privkey.pem	Private key for the Postfix server.
users.txt	Mail account credentials to create at startup.

Building from source

Build the image locally using this git repository as the build context:

docker build \
  --build-arg VERSION=0.0.4 \
  --tag cisagov/postfix:0.0.4 \
  https://github.com/cisagov/postfix-docker.git#develop

Cross-platform builds

To create images that are compatible with other platforms, you can use the buildx feature of Docker:

1. Copy the project to your machine using the Code button above or the command line:

   git clone https://github.com/cisagov/postfix-docker.git
   cd postfix-docker

2. Create the Dockerfile-x file with buildx platform support:

   ./buildx-dockerfile.sh

3. Build the image using buildx:

   docker buildx build \
     --file Dockerfile-x \
     --platform linux/amd64 \
     --build-arg VERSION=0.0.4 \
     --output type=docker \
     --tag cisagov/postfix:0.0.4 .

Contributing

We welcome contributions! Please see CONTRIBUTING.md for details.

License

This project is in the worldwide public domain.

This project is in the public domain within the United States, and copyright and related rights in the work worldwide are waived through the CC0 1.0 Universal public domain dedication.

All contributions to this project will be released under the CC0 dedication. By submitting a pull request, you are agreeing to comply with this waiver of copyright interest.