Since some time now I have been working on migrating my SMTP relay docker image to use alpine linux as the base image. This change was something I was wanting to do for some time but what really triggered it was that the current version is CentOS 7 based and uses supervisord to handle container processes. CentOS 8 removed supervisor, so I was somewhat forced to go ahead with this migration if I wanted to continue to use supervisor.
The migration to alpine linux has several advantages, one is the reduced image size we get, going from 114MB for the CentOS 7 based image to 30MB for the alpine linux one, another is that supervisor still can be used. Another change I want to do in the near future is to move to a more container oriented init system, like s6-overlay or dumb-init.
So if you want to test out the new alpine based image you can use juanluisbaptiste/postfix:alpine, and checkout the code on this branch. As there haven’t been many issues with this version soon I will be switching the latest tag from the current CentOS image to this new one to leave it as the main image.
Lastly, a PR was accepted to add docker secrets support for the SMTP password. Now you can use a file to set the value of the SMTP_PASSWORD variable without using environment variables for increased security. Checkout the documentation on the README file for instructions on how to use this feature.