Merging existing mailboxes to aliases

I am trying to merge all, existing or not, different mailboxes in one with the mailbox alias plugin. If I add the following lines, will the existing mailboxes automatically merge in one mailbox and corresponding links auto create? If not, do I have to do this manually?

mailbox_alias_new = Spam mailbox_alias_new2 = Junk E-mail mailbox_alias_new3 = Sent Items mailbox_alias_new4 = Sent Messages mailbox_alias_new5 = Deleted Items mailbox_alias_old = Junk mailbox_alias_old2 = Junk mailbox_alias_old3 = Sent mailbox_alias_old4 = Sent mailbox_alias_old5 = Trash

Lefteris