Postfix is a service which forks itself and runs in the background. Postfix version 3.3.0 added container support. There was an issue where Postfix could not run as PID=1, and it was swiftly fixed in version 3.3.1 As I could not find any official Docker image for the latest versin of Postfix, I decided to build one myself. At the time I built the image, there was no Debian package available so I had to compile the package from source. Here is the link to the Dockerfile. You can build the docker image yourselves and use it too. Just run git clone https://github.com/EasyEngine/dockerfiles.git cd postfix docker build -t postfix . # Now run the docker image using docker run \ -h example.com \ -p 1025:25 \ -v "/dev/log:/dev/log" postfix Now you can point in the smtp settings to use localhost:1025. The logs will be available at /var/log/mail.log on your host.