If you’re moving a legacy email archive to Office 365, chances are good that you also have Exchange journal data to move as well. If you do, it’s likely that the total amount of journal data is equal to or greater than the total size of your email archive.
With regards to Office 365, you might be wondering where the journal data is stored. It comes down to two possibilities; move the journal into the Personal Archive of an Office 365 active mailbox, or create separate Office 365 mailboxes (e.g. Journal Mail 001, Journal Mail 002, Journal Mail 003) and move the journal data for groups of custodians into those. This practice is called "journal splitting”. To many, an unknown concept that raises many questions, the most important being; is journal splitting the best practice for your organization’s regulatory or legal needs? The answer is it depends… Let’s break it down so you have all the facts before you make a migration decision on your journal.