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Postfix Image for SMTP Auth

Available tags: latest.

This image is a CentOS 7 container running postfix preconfigured for SMTP relay authentication. It runs as an open relay mail server inside the Docker Containers internal network, so it can be used by any container to send emails through the remote relay.

The hostname of the postfix server is set in the environment variable MTP_HOST and is mandatory. Postfix will run as an open relay server only if the variables below are also set.

The relay is set in MTP_RELAY and the port in MTP_PORT.

The .secrets file should be used as a runtime environment variables, to set the user and password required for SMTP authentication by the MTP_RELAY:


Basic way to get one instance up and running:

docker run --rm  -t -i -e --env-file=.secret -v /etc/localtime:/etc/localtime:ro --name=postfix eeacms/postfix 

From the application container, running on the same docker host, one can set the SMTP server to the postfix container address.

Using the mount directive -v /etc/localtime:/etc/localtime:ro will make sure that the postfix container will share same timezone as the host, so that the emails have correct date and timestamps.

Example usage

In the example folder, there is an example centos container than can be used to test connectivity.

cd example
docker build -t example .
docker run --rm -it -v /etc/localtime:/etc/localtime:ro --link=postfix:postfixcontainer example

# from commandline:
$ mail

# from an application, python:
$ python
Python 2.6.6 (r266:84292, Jan 22 2014, 09:42:36) 
[GCC 4.4.7 20120313 (Red Hat 4.4.7-4)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import smtplib
>>> s = smtplib.SMTP('postfixcontainer')
>>> s.sendmail('', [''], 'test')

Existing container configuration

If you have an existing container that makes use of /usr/bin/sendmail to send emails, and you want to use this postfix image instead, you must modify your Dockerfile to :

Install mailx/ssmtp:

# RUN apt-get install -y mailx ssmtp
# RUN yum install -y mailx ssmtp

Modify and copy / mount the /etc/ssmtp.conf file (see: Change mailhub directive to the name of the postfixcontainer.

# ADD ssmtp.conf /etc/ssmtp.conf

You can check the example image for more details.

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