smtp-relay

This image provides an SMTP relay host for emails from within a Kubernetes cluster.

Configure this container to use an upstream authenticated SMTP relay like SendGrid or your ISP's mail server, and provide an open relay service to your cluster. This means you don't have to configure all of your containerised services with email auth secrets.

Config

This image supports the following enironment variables. All are required.

Variable	Use	Example
SMTP_RELAY_HOST	Hostname of upstream SMTP relay server	[smtp.sendgrid.net]:587
SMTP_RELAY_USERNAME	Username for upstream SMTP relay server	apikey
SMTP_RELAY_PASSWORD	Password for upstream SMTP relay server	pAsSwOrD
SMTP_RELAY_MYHOSTNAME	Hostname of this SMTP relay	smtp-relay.yourhost.com
SMTP_RELAY_MYNETWORKS	Comma-separated list of local networks that can use this SMTP relay	127.0.0.0/8,10.0.0.0/8
SMTP_RELAY_WRAPPERMODE	Request postfix connects using SUBMISSIONS/SMTPS protocol instead of STARTTLS	no
SMTP_TLS_SECURITY_LEVEL	default SMTP TLS security level for the Postfix SMTP client	""
SMTP_USE_TLS	Define TLS usage to secure communication between mail servers	no
SMTP_MESSAGE_SIZE_LIMIT	default SMTP message_size_limit (Example: 10MB)	10240000

Quickstart

Run on docker

docker run --rm -it -p 2525:25 \
	-e SMTP_RELAY_HOST="[smtp.sendgrid.net]:587" \
	-e SMTP_RELAY_MYHOSTNAME=smtp-relay.yourhost.com \
	-e SMTP_RELAY_USERNAME=username \
	-e SMTP_RELAY_PASSWORD=password \
	-e SMTP_RELAY_MYNETWORKS=127.0.0.0/8,10.0.0.0/8 \
	-e SMTP_RELAY_WRAPPERMODE=no \
	-e SMTP_TLS_SECURITY_LEVEL="" \
	-e SMTP_MESSAGE_SIZE_LIMIT=10240000 \
	djjudas21/smtp-relay

Send a test message

telnet localhost 2525
220 smtp-relay.yourhost.com ESMTP Postfix
helo localhost
250 smtp-relay.yourhost.com
mail from: noreply@yourhost.com
250 2.1.0 Ok
rcpt to: chris@applariat.com
250 2.1.5 Ok
data
354 End data with .
Subject: What?
My hovercraft is full of eels.
.
250 2.0.0 Ok: queued as 982FF53C
quit
221 2.0.0 Bye
Connection closed by foreign host