Are you using Journaling in a mixed Exchange 2007 and Exchange 2003 environment? Regardless of the journaling method used, you would need to enable an entire mailbox database for journaling, resulting in mail to and from all mailboxes on the database being journaled. Exchange 2003 servers transmit journaling metadata between them in a special binary large object (BLOB) using the XEXCH50 extension during an SMTP conversation. In Exchange 2007, message-only journaling and Bcc journaling are no longer supported because they do not capture all the information necessary in today’s compliance-focused environments. The only option is envelope journaling.

More info: Exchange Team