docker-postfix

Simple Postfix SMTP TLS relay docker image with no local authentication enabled (to be run in a secure LAN).

Build instructions

Clone this repo and then:

cd docker-Postfix
sudo docker build -t postfix .

You can also find a prebuilt docker image from Docker Hub, which can be pulled with this command:

sudo docker pull juanluisbaptiste/postfix:latest

How to run it

The following env variables need to be passed to the container:

• SMTP_SERVER Server address of the SMTP server to use.
• SMTP_USERNAME Username to authenticate with.
• SMTP_PASSWORD Password of the SMTP user.

To use this container from anywhere, the 25 port needs to be exposed to the docker host server:

docker run -d --name postfix -p "25:25"  \ 
       -e SMTP_SERVER=smtp.bar.com \
       -e SMTP_USERNAME=foo@bar.com \
       -e SMTP_PASSWORD=XXXXXXXX \
       juanuisbaptiste/postfix

If you are going to use this container from other docker containers then it's better to just publish the port:

docker run -d --name postfix -P \
       -e SMTP_SERVER=smtp.bar.com \
       -e SMTP_USERNAME=foo@bar.com \
       -e SMTP_PASSWORD=XXXXXXXX \
       juanuisbaptiste/postfix

A note about using gmail as a relay

Since last year, Gmail by default does not allow email clients that don't use OAUTH 2 for authentication (like Thunderbird or Outlook). First you need to enable access to "Less secure apps" on your google settings.

Also take into account that email From: header will contain the email address of the account being used to authenticate against the Gmail SMTP server(SMTP_USERNAME), the one on the email will be ignored by Gmail.