mezz64/docker-postfix repository overview

⁠docker-postfix

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

It also includes rsyslog to enable logging to stdout.

⁠Build instructions

Clone this repo and then:

cd docker-Postfix
sudo docker build -t postfix .

Or you can use the provided docker-compose⁠ files:

sudo docker-compose -f docker-compose.yml -f docker-compose.dev.yml build

For more information on using multiple compose files see here⁠. 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_PORT (Optional, Default value: 587) Port address of the SMTP server to use.
• SMTP_USERNAME Username to authenticate with.
• SMTP_PASSWORD Password of the SMTP user.
• SERVER_HOSTNAME Server hostname for the Postfix container. Emails will appear to come from the hostname's domain.
• MYNETWORKS Subnets from which relaying is allowed, if empty only the containers itself can relay. Escape the mask with a backslash.

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 [email protected] \
       -e SMTP_PASSWORD=XXXXXXXX \
       -e SERVER_HOSTNAME=helpdesk.mycompany.com \
       -e MYNETWORKS=192.168.1.0\/24
       juanluisbaptiste/postfix

Note the backslash used to escape the subnet mask.

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 [email protected] \
       -e SMTP_PASSWORD=XXXXXXXX \
       -e SERVER_HOSTNAME=helpdesk.mycompany.com \           
       juanluisbaptiste/postfix

Or if you can start the service using the provided docker-compose⁠ file for production use:

sudo docker-compose up -d

⁠A note about using gmail as a relay

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.

⁠Debugging

If you need troubleshooting the container you can set the environment variable DEBUG=yes for a more verbose output.