Why new e-mails from the same person don't create separate cases, but arrive in one conversation?

[Paulina Zakrzewska]

Why new e-mails from the same person don't create separate cases, but arrive in one conversation? The person, who write new e-mails - change the titel, write them as new e-mails, not as answer on existing one, but everything arrives in one communication. Then we have to manually create separate cases. Please clarify why the separate cases aren't created automatically.