It's usually configured correctly at some point in time and then the configuration "rots": it becomes inconsistent, some emails are forwarded, other are lost, nobody cares, etc.
In my case, I configured Postfix to redirect all mails looking like (root|admin|postmaster)@server to myemailaddress+(root|admin|postmaster)_server@domain and Postfix ignores what comes after the + in the user part. So I get all the emails but I still know where they come from. It has worked well for quite some years now but I'm not deluding myself, I know that at some time, that will rot too.
In my case, I configured Postfix to redirect all mails looking like (root|admin|postmaster)@server to myemailaddress+(root|admin|postmaster)_server@domain and Postfix ignores what comes after the + in the user part. So I get all the emails but I still know where they come from. It has worked well for quite some years now but I'm not deluding myself, I know that at some time, that will rot too.