Redmine

Hi Everybody,
First of all, I want to apologize if I am wrong about that feature.

Some of our redmine users have set up their mail notification settings with the option
Only for things I watch or I'm involved in.
Once logs correctly set up, I can identify which (and when) mails are sent or not.

What we are thinking about this option is once we have been involved in a task (I mean assigned to)
we will then be notified for any changes (even if we are not watcher).

But it appears a mail is sent to user only when he/she is assigned to.
If this is the expected behavior, is there any configuration enabling the behavior I described ?

Redmine version: 3.4.2 stable.

Thanks you for any feedback.
Regards,
Nicolas