I am using a Synology KMU NAS. On that NAS I have installed the GitLab Docker container that seems to have a bug. That bug causes the Software to refuse to send administrative e-mails without authentication. There is an environment variable SMTP_AUTHENTICATION that is passed to GitLab but it seems the non-authenticated configuration (supported by omnibus-gitlab according to the maintainer) is not passed correctly and falls back to "Login" instead.
Since our central IT service provides an un-authenticated SMTP server only (at least for non-personal use), I need to take care of the problem until Synology (maybe) fixes the problem in the future.
My idea is to modify the docker container so it passes the proper options to GitLab. I guess the error is trivial. However I have never used Docker containers before.
Is there a way to modify the docker container? What do I need to do?