Problem with sending email by using SMTP

Thank you for your reply, Mr. alfredb. Below is my docker-compose.yml file:

After reading your reply, I have a few more questions:

  1. Since you mentioned that after setting up Kanboard using Docker (version 1.2.42, correct?), you were able to configure SMTP for email sending, could you please provide the system specifications of the computer you used (e.g., operating system, CPU, etc.), and the process you followed to set up Kanboard with Docker? I would like to know all the commands (history) you ran during the setup. You can check the history of commands by running history on the server (terminal), which should show all the commands executed during the installation of Kanboard. Could you please send me a screenshot of those commands along with your docker-compose.yml file?
    (My Kanboard installation process was: First, I ran “docker pull kanboard/kanboard”, then I wrote my own docker-compose.yml file, followed by “docker-compose up -d” to bring up Kanboard. After that, I imported the data, files, and user accounts into Kanboard as shown in the image. For the data, plugins, config.php, and MariaDB, I first placed them on the host machine and then mapped them to the corresponding folders in Docker.)

  2. If I modify the content in the config.php file, do I need to restart Docker using docker restart kanboard or docker-compose restart kanboard?

  3. Kanboard should have logs for email sending. Where would these logs be stored in Docker? If I check these logs, will they show what went wrong with the SMTP email sending?