### Production Deployment with docker-compose.yml

Source: https://context7.com/juanluisbaptiste/docker-postfix/llms.txt

Deploy Postfix in production using a `docker-compose.yml` file. This setup reads configuration from a `.env` file, ensures the container always restarts, and mounts the host's `/etc/localtime` for accurate log timestamps. Start in production mode with `docker compose up -d` and view logs with `docker logs -f postfix`.

```yaml
# docker-compose.yml
name: postfix
services:
  postfix:
    image: juanluisbaptiste/postfix:latest
    expose:
      - "25"
    env_file:
      - .env
    restart: always
    volumes:
      - "/etc/localtime:/etc/localtime:ro"
```

```bash
# Copy and configure the env file
cp .env.example .env
# Edit .env with your SMTP credentials:
# SMTP_SERVER=smtp.bar.com
# SMTP_USERNAME=foo@bar.com
# SMTP_PASSWORD=supersecretpassword
# SERVER_HOSTNAME=helpdesk.mycompany.com

# Start in production mode
docker compose up -d

# View real-time mail logs
docker logs -f postfix
```

--------------------------------

### Configure SMTP Password from File

Source: https://github.com/juanluisbaptiste/docker-postfix/blob/master/README.md

Example of mounting a password file into the container to avoid exposing sensitive credentials in environment variables.

```bash
-e SMTP_PASSWORD_FILE=/secrets/smtp_password
-v $(pwd)/secrets/:/secrets/
```

--------------------------------

### Configure SMTP Username from File

Source: https://github.com/juanluisbaptiste/docker-postfix/blob/master/README.md

Example of mounting a username file into the container to avoid exposing sensitive credentials in environment variables.

```bash
-e SMTP_USERNAME_FILE=/secrets/smtp_username
-v $(pwd)/secrets/:/secrets/
```

--------------------------------

### Docker Compose for Production

Source: https://github.com/juanluisbaptiste/docker-postfix/blob/master/README.md

Command to start the Postfix container in detached mode using Docker Compose, recommended for production environments.

```bash
sudo docker-compose up -d
```

--------------------------------

### Run Basic SMTP Relay Container

Source: https://context7.com/juanluisbaptiste/docker-postfix/llms.txt

Starts a Postfix relay container exposing port 25 and connecting to an upstream SMTP server with TLS and SASL authentication. Verify the container and Postfix startup using `docker logs`.

```bash
docker run -d --name postfix -p "25:25" \
  -e SMTP_SERVER=smtp.bar.com \
  -e SMTP_PORT=587 \
  -e SMTP_USERNAME=foo@bar.com \
  -e SMTP_PASSWORD=supersecretpassword \
  -e SERVER_HOSTNAME=helpdesk.mycompany.com \
  juanluisbaptiste/postfix:latest

# Verify container is running and Postfix started successfully
docker logs postfix
# Expected output includes lines like:
# Setting configuration option myhostname with value: helpdesk.mycompany.com
# Setting configuration option relayhost with value: [smtp.bar.com]:587
# Adding SASL authentication configuration
# postfix/master[1]: daemon started -- version 3.x.x, configuration /etc/postfix
```

--------------------------------

### Configure SMTP Networks

Source: https://github.com/juanluisbaptiste/docker-postfix/blob/master/README.md

Example of setting the SMTP_NETWORKS environment variable to allow specific subnets to use the relay. Note: This requires host network mode.

```bash
-e `SMTP_NETWORKS='xxx.xxx.xxx.xxx/xx,xxx.xxx.xxx.xxx/xx'`
```

--------------------------------

### Build Docker Image from Source

Source: https://context7.com/juanluisbaptiste/docker-postfix/llms.txt

Build the Postfix Docker image locally using the provided `Dockerfile` and an override Compose file for local development. Clone the repository, navigate to the directory, and use `docker build` or `docker compose` commands.

```bash
# Clone and build manually
git clone https://github.com/juanluisbaptiste/docker-postfix.git
cd docker-postfix

# Direct Docker build
docker build -t juanluisbaptiste/postfix:local .

# Or use the override compose file (builds with :dev tag)
docker compose -f docker-compose.yml -f docker-compose.override.yml build
```

--------------------------------

### Build Docker Postfix Image

Source: https://github.com/juanluisbaptiste/docker-postfix/blob/master/README.md

Build the Docker image locally from the cloned repository. Ensure you are in the 'docker-Postfix' directory.

```bash
cd docker-Postfix
sudo docker build -t juanluisbaptiste/postfix .

```

--------------------------------

### Run Docker Postfix Container (Publish All Ports)

Source: https://github.com/juanluisbaptiste/docker-postfix/blob/master/README.md

Command to run the Postfix container and publish all exposed ports, useful for inter-container communication.

```bash
docker run -d --name postfix -P \
           -e SMTP_SERVER=smtp.bar.com \
           -e SMTP_USERNAME=foo@bar.com \
           -e SMTP_PASSWORD=XXXXXXXX \
           -e SERVER_HOSTNAME=helpdesk.mycompany.com \
           juanluisbaptiste/postfix
```

--------------------------------

### View Postfix Logs in Real Time

Source: https://github.com/juanluisbaptiste/docker-postfix/blob/master/README.md

Command to follow the logs of the running Postfix container in real time, useful for monitoring and debugging.

```bash
docker logs -f postfix
```

--------------------------------

### Build Docker Postfix Image with Docker Compose

Source: https://github.com/juanluisbaptiste/docker-postfix/blob/master/README.md

Build the Docker image using Docker Compose. This is an alternative to the direct docker build command.

```bash
sudo docker-compose build

```

--------------------------------

### Configure SMTP Server and Hostname

Source: https://context7.com/juanluisbaptiste/docker-postfix/llms.txt

Demonstrates the required `SMTP_SERVER` and `SERVER_HOSTNAME` environment variables. The container will exit with an error if these are not set. `mydomain` is derived from `SERVER_HOSTNAME` unless `DOMAIN` is specified.

```bash
# Container will fail fast with a clear error if required vars are missing
docker run --rm \
  -e SMTP_SERVER=smtp.sendgrid.net \
  juanluisbaptiste/postfix:latest
# Output: SERVER_HOSTNAME is not set  (exits with code 1)

# Correct usage
docker run -d --name postfix -p "25:25" \
  -e SMTP_SERVER=smtp.sendgrid.net \
  -e SMTP_PORT=587 \
  -e SMTP_USERNAME=apikey \
  -e SMTP_PASSWORD=SG.xxxxxxxxxxxx \
  -e SERVER_HOSTNAME=app.mycompany.com \
  juanluisbaptiste/postfix:latest
# Postfix mydomain will be automatically set to "mycompany.com"
```

--------------------------------

### Use Secret Files for Credentials

Source: https://context7.com/juanluisbaptiste/docker-postfix/llms.txt

Recommends using `SMTP_USERNAME_FILE` and `SMTP_PASSWORD_FILE` for production and Kubernetes deployments to avoid plain-text environment variables. Ensure file permissions are set to `600`.

```bash
# Create secret files on the host
mkdir -p ./secrets
echo "foo@bar.com"      > ./secrets/smtp_username
echo "supersecretpass"  > ./secrets/smtp_password
chmod 600 ./secrets/*

# Run with file-based credentials
docker run -d --name postfix -p "25:25" \
  -e SMTP_SERVER=smtp.bar.com \
  -e SERVER_HOSTNAME=helpdesk.mycompany.com \
  -e SMTP_USERNAME_FILE=/secrets/smtp_username \
  -e SMTP_PASSWORD_FILE=/secrets/smtp_password \
  -v "$(pwd)/secrets:/secrets:ro" \
  juanluisbaptiste/postfix:latest

# In Kubernetes, use a Secret volume mount and reference the mount path:
# env:
#   - name: SMTP_SERVER
#     value: "smtp.bar.com"
#   - name: SMTP_PASSWORD_FILE
#     value: "/secrets/smtp_password"
# volumeMounts:
#   - name: smtp-secret
#     mountPath: /secrets
#     readOnly: true
```

--------------------------------

### Send Test Email from Host

Source: https://context7.com/juanluisbaptiste/docker-postfix/llms.txt

Send a test email from the host machine to the running Postfix relay. Ensure port 25 is exposed from the container to the host.

```bash
echo "Test body" | mailx -s "Test Subject" \
  -S smtp=smtp://localhost:25 \
  -S from=sender@mycompany.com \
  recipient@example.com
```

--------------------------------

### Pull Docker Postfix Image from Docker Hub

Source: https://github.com/juanluisbaptiste/docker-postfix/blob/master/README.md

Pull the latest prebuilt Docker image for Postfix from Docker Hub. This is the recommended way to use the image if you don't need to build it yourself.

```bash
sudo docker pull juanluisbaptiste/postfix:latest

```

--------------------------------

### Configure Logging, Message Size, Encoding, and Timezone

Source: https://context7.com/juanluisbaptiste/docker-postfix/llms.txt

Configure miscellaneous settings like logging subjects, message size limits, SMTPUTF8 encoding, header addition, and timezone using environment variables. Monitor logs including subject lines with `docker logs -f postfix`.

```bash
docker run -d --name postfix -p "25:25" \
  -e SMTP_SERVER=smtp.bar.com \
  -e SMTP_USERNAME=foo@bar.com \
  -e SMTP_PASSWORD=mypassword \
  -e SERVER_HOSTNAME=app.mycompany.com \
  -e LOG_SUBJECT=yes \
  -e MESSAGE_SIZE_LIMIT=20480000 \
  -e SMTPUTF8_ENABLE=no \
  -e ALWAYS_ADD_MISSING_HEADERS=yes \
  -e TZ=America/New_York \
  juanluisbaptiste/postfix:latest

# Monitor logs including subject lines:
docker logs -f postfix
```

--------------------------------

### Run Docker Postfix Container

Source: https://github.com/juanluisbaptiste/docker-postfix/blob/master/README.md

Basic command to run the Postfix container, exposing port 25 and setting essential environment variables for SMTP relay.

```bash
docker run -d --name postfix -p "25:25" \
           -e SMTP_SERVER=smtp.bar.com \
           -e SMTP_USERNAME=foo@bar.com \
           -e SMTP_PASSWORD=XXXXXXXX \
           -e SERVER_HOSTNAME=helpdesk.mycompany.com \
           juanluisbaptiste/postfix
```

--------------------------------

### Enable Debugging Output

Source: https://github.com/juanluisbaptiste/docker-postfix/blob/master/README.md

Set the DEBUG environment variable to 'yes' to enable verbose output for troubleshooting the container.

```bash
_DEBUG=yes
```

--------------------------------

### Enable Debug Output for Postfix Relay

Source: https://context7.com/juanluisbaptiste/docker-postfix/llms.txt

Run the Postfix container with debug enabled to see detailed logs of the run.sh script execution. This is useful for troubleshooting configuration issues.

```bash
docker run -d --name postfix-debug -p "25:25" \
  -e SMTP_SERVER=smtp.bar.com \
  -e SMTP_USERNAME=foo@bar.com \
  -e SMTP_PASSWORD=mypassword \
  -e SERVER_HOSTNAME=helpdesk.mycompany.com \
  -e DEBUG=yes \
  juanluisbaptiste/postfix:local

docker logs -f postfix-debug
```

--------------------------------

### Send Test Email from Another Docker Container

Source: https://context7.com/juanluisbaptiste/docker-postfix/llms.txt

Send a test email from a temporary Alpine container connected to the same Docker network as the Postfix relay. This verifies inter-container communication.

```bash
docker run --rm --network container:postfix alpine sh -c \
  "apk add --no-cache mailx && \
   echo 'Test body' | mailx -s 'Hello' \
     -S smtp=smtp://postfix:25 \
     -S from=app@mycompany.com \
     recipient@example.com"
```

--------------------------------

### Configure Port 465 for SMTPS (Implicit TLS)

Source: https://context7.com/juanluisbaptiste/docker-postfix/llms.txt

When `SMTP_PORT` is set to `465`, the container automatically configures Postfix for implicit TLS (SMTPS) by enabling `smtp_tls_wrappermode = yes` and `smtp_tls_security_level = encrypt`. The default port is `587` for STARTTLS.

```bash
# Relay via SMTPS (implicit TLS on port 465)
docker run -d --name postfix -p "25:25" \
  -e SMTP_SERVER=smtp.example.com \
  -e SMTP_PORT=465 \
  -e SMTP_USERNAME=user@example.com \
  -e SMTP_PASSWORD=mypassword \
  -e SERVER_HOSTNAME=relay.mycompany.com \
  juanluisbaptiste/postfix:latest

# Logs will confirm:
# Setting configuration option smtp_tls_wrappermode with value: yes
# Setting configuration option smtp_tls_security_level with value: encrypt
```

--------------------------------

### Rewrite From Header with OVERWRITE_FROM

Source: https://context7.com/juanluisbaptiste/docker-postfix/llms.txt

Use the `OVERWRITE_FROM` environment variable to rewrite the `From:` header and `sender_canonical_maps` for all relayed messages. This is useful when an upstream SMTP provider requires the authenticated account address.

```bash
# Rewrite all outgoing From: headers to a single address
docker run -d --name postfix -p "25:25" \
  -e SMTP_SERVER=smtp.gmail.com \
  -e SMTP_PORT=587 \
  -e SMTP_USERNAME=noreply@mycompany.com \
  -e SMTP_PASSWORD=apppassword \
  -e SERVER_HOSTNAME=app.mycompany.com \
  -e 'OVERWRITE_FROM=No Reply <noreply@mycompany.com>' \
  juanluisbaptiste/postfix:latest

# All emails relayed will have their From header replaced:
# Before: From: user@internal.lan
# After:  From: No Reply <noreply@mycompany.com>
```

--------------------------------

### Expand Allowed Networks with SMTP_NETWORKS

Source: https://context7.com/juanluisbaptiste/docker-postfix/llms.txt

Append additional IPv4 or IPv6 CIDR ranges to the default `mynetworks` using the `SMTP_NETWORKS` environment variable. This requires the container to run with Docker host networking (`--network host`).

```bash
# Add extra IPv4 and IPv6 subnets (requires host network mode)
docker run -d --name postfix --network host \
  -e SMTP_SERVER=smtp.bar.com \
  -e SMTP_USERNAME=foo@bar.com \
  -e SMTP_PASSWORD=mypassword \
  -e SERVER_HOSTNAME=relay.mycompany.com \
  -e SMTP_NETWORKS='203.0.113.0/24,2001:db8::/32' \
  juanluisbaptiste/postfix:latest

# Resulting Postfix mynetworks will be:
# 10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16, 203.0.113.0/24, [2001:db8::]/32
```

--------------------------------

### Add Relay Tracking Header with SMTP_HEADER_TAG

Source: https://context7.com/juanluisbaptiste/docker-postfix/llms.txt

Prepend a custom `RelayTag:` header to outgoing emails using the `SMTP_HEADER_TAG` environment variable. This helps identify which relay instance handled a message for troubleshooting.

```bash
docker run -d --name postfix -p "25:25" \
  -e SMTP_SERVER=smtp.bar.com \
  -e SMTP_USERNAME=foo@bar.com \
  -e SMTP_PASSWORD=mypassword \
  -e SERVER_HOSTNAME=helpdesk.mycompany.com \
  -e SMTP_HEADER_TAG=PROD-RELAY-01 \
  juanluisbaptiste/postfix:latest

# Outgoing emails will contain additional headers:
# RelayTag: PROD-RELAY-01
# MIME-Version: 1.0
# ...
```

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