Archiving From Exchange
From Roaring Penguin
Archiving from an Exchange server?
Message journaling is used to get the mails into the archive if you aren't using CanIt for outbound mail.
(It will archive mails that pass through the server via SMTP, but if your mail is not passing through on its way out, then message journaling is what you want.)
To find out more about this, go to the Archiver tab, select the "Authorized Host" or "Authorized Secrets" option and then select "Online Documentation" link in the upper right.
This will link you to our documentation which discusses mail journaling options.