MailArchiva is a powerful, full featured email archiving (email archiver) and compliance solution for mail systems such as Microsoft Exchange. It stores all incoming, outgoing and internal emails for long term storage. A web based user interface is avail
userb emails usera - usera does not have userb on their whitelist.
Userb's email is not delivered, instead userb gets a mail asking if they wish to appear on usera's list? if yes usera gets asked same thing if yes all old/new mails get delivered