Postfix relay running in Kubernetes

This repository has an example of a postfix relay running in Kubernetes using a helm chart.

Build Docker image

You can build the Docker image locally

# For local build
docker build -t test/postfix-relay:0.1 .

# Multi arch build and push
docker buildx build --platform linux/amd64,linux/arm64 -t test/postfix-relay:0.1  --push .

Run locally with Docker

Run the postfix relay locally for testing

# Need to set SMTP connection details
export SMTP=""
export USERNAME_TEST=<your smtp username>
export PASSWORD_TEST=<your smtp password>

# Optional custom configuration to add/override in /etc/postfix/main.cf (delimited by a ";")
export POSTFIX_CUSTOM_CONFIG="key1 = value1;key2 = value2;key3 = value3"

# Set list of allowed networks
export TX_SMTP_RELAY_NETWORKS='10.0.0.0/8,127.0.0.0/8,172.17.0.0/16,192.0.0.0/8'

docker run --rm -d --name postfix-relay -p 25:25 \
	-e TX_SMTP_RELAY_HOST="" \
	-e TX_SMTP_RELAY_MYHOSTNAME=my.local \
	-e TX_SMTP_RELAY_USERNAME=${USERNAME_TEST} \
	-e TX_SMTP_RELAY_PASSWORD=${PASSWORD_TEST} \
	-e TX_SMTP_RELAY_NETWORKS=${TX_SMTP_RELAY_NETWORKS} \
	-e POSTFIX_CUSTOM_CONFIG="${POSTFIX_CUSTOM_CONFIG}" \
	test/postfix-relay:0.1

Test sending mail

1. Connect to running container on port 2525

telnet localhost 25

2. Edit the following with your details and paste in your terminal

helo localhost
mail from: [email protected]
rcpt to: [email protected]
data
Subject: Subject here...
The true story of swans singing Pink Floyd. 
.
quit

3. You should see the following

220 tx-smtp-relay.example.com ESMTP Postfix
helo localhost
250 tx-smtp-relay.example.com
mail from: [email protected]
250 2.1.0 Ok
rcpt to: [email protected]
250 2.1.5 Ok
data
354 End data with <CR><LF>.<CR><LF>
Subject: Subject here...
The true story of swans singing Pink Floyd. 
.
250 2.0.0 Ok: queued as 982FF53C
quit
221 2.0.0 Bye
Connection closed by foreign host

4. Check the inbox of [email protected] and see you got the email.

Deploy Helm Chart

The Helm Chart in helm/postfix directory can be used to deploy the postfix-relay into your Kubernetes cluster.

Create a custom-values.yaml with the configuration details

dkim:
  disable: false
  canonicalization: "simple"
  selector: "default"
smtp:
  relayHost: ""
  relayMyhostname: <your smtp hostname>
  relayUsername: <your smtp username>
  relayPassword: <your smtp password>
  relayNetworks: '10.0.0.0/8,127.0.0.0/8,172.17.0.0/16,192.0.0.0/8'

Deploy postfix

helm upgrade --install postfix-relay helm/postfix -f custom-values.yaml

Postfix Metrics exporter

An optional postfix-exporter sidecar can be deployed for exposing postfix metrics. This is using the work from https://github.com/kumina/postfix_exporter.

To enable the exporter sidecar, update your custom-values.yaml file and add

# Enable the postfix-exporter sidecar
exporter:
  enabled: true

# Enable a ServiceMonitor object for Prometheus scraping
serviceMonitor:
  enabled: true

Deploy postfix

helm upgrade --install postfix-relay helm/postfix -f custom-values.yaml