Exchange 2007 deleted item retention

in Exchange 2007 there is a setting under deleted item retention which says “Do not permanently delte items until you backup the database”

Now I have 3 questions about this.

1. Can this be done on all the mailboxs rather then indivisual mailbox?

2. how does exchange know that its been backup specally when everyone use third party backup softwares.

3. does this still apply if i delete the email 5 mins after I have recieved?

My exchange 07 is running on 2003 server

any help would be appriciated