As a new OpenProject administrator I salute you dear OpenProject users,

What is the problem?

I'm having trouble sending e-mail to project members when I mention select them as an assignee, owner or add them into a project.

Update;

Ok. I am figuring out that what I am asking is not possible though only if user watches the task, there will be an e-mail sent.

So I think that what my trouble would not be possibly resolved with the version(OpenProject 12.0.8) I am working with.

What I have done?

1. I've manually added users from my organisation to my OpenProject build.
2. I've checked if any of them have its notification closed. It was not.
3. I tested the "Incoming & Outgoing > E-mail Notifications > Send a Test E-mail"(I am using Turkish version so the terms might not be translated accurately) and It worked, I've got a test e-mail.
4. I've activated all users "E-mail Reminders > ✓ Immediately when someone @mentions me". This is working as intended.
5. I've searched the forum with the key words; "e-mail notification", "e-mail" and "notification" but I couldn't find the answer.
6. I've tested that they are having notification in softwares interface but not in e-mail form.
7. (edit) I've decreased the number 5 to 0 in "Inbound&Outgoing" > "Settings" > "User actions aggregated within". And It didn't help.