[redmine] “Email delivery is not configured” error

If you get this error on Redmine‘s email notification configuration page:

Email delivery is not configured, and notifications are disabled. Configure your SMTP server in config/email.yml and restart the application to enable them.

you did configure config/email.yml file, and you did restart the application, and this message is still showing in the administration panel, you can try placing the email.yml file in other directory. For me, it helped when I placed it in /etc/redmine/default/, where Debian keeps YAML configuration files for Redmine installation instances. If you run multiple instances on one host, you may have to change default subdirectory name to the instance name.
I’m writing this post because while the solution is trivial, I’ve noticed that many questions about this error on Redmine’s forum remains unanswered.