Journaling in Microsoft Exchange
Journaling is the process of recording all email communications, whereas archiving involves backing up this email data in another location other than an email server like MS Exchange.
As this posting to Microsoft's TechNet's site makes clear, Office 365 allows an admin to set rules which control how emails are journaled. Up to ten rules can be set. It is possible to record only emails sent to outside parties, or just record emails sent internally. The SMTP addresses or individual recipients can be targeted.
Exchange allows for Unified Messaging which consolidates email, voicemail, and faxes. It is possible to exclude the journaling of voicemail messages, but if these are excluded faxes will still be retained.
Online Exchange mailboxes cannot be used to receive journaling reports. These must be sent to an internal archiving system.