Best way to move spam mail to a folder readable by users

[astate]

I search the best way to move spam mail to a folder readable by users.

On other server.. i have email spam@domaine.com and alll spam are go on it.
But i don't know how i can install it with ispconfig and postfix

I use SquirelMail, because it's on installation by default. I use the Centos OS.
On other server i use roundcube.
It's possible to easy add pluggin in squirelmail ? Because i dont want scrap ispconfig.