Spring Boot - external property not found

My application is trying to externalize all project properties, some ones will be inside my app and another ones will be in a folder somewhere in Windows.

I set up Spring to execute this way: --spring.config.location=http://file/C:\Temp\config\application.properties,classpath:application.properties

As you can see, if the same property exists in both sides, application property will be kept (priority order). I noticed for example some properties such as "server.port" can be found if exists outside folder (file://) but if I create one such "common.acronym-name" my project can not find its value.

Why "server.port" has a different behaviour that one create by me? Is there any configuration I need to tell Spring Boot to see this external property in my project?

@Value("${common.acronym-name:}") //Just find it in application classpath
private String acronymEnv;

Thanks!