Before you start moving files around, make sure you have a current backup of your mail.
Back Up Data Using Time Machine
Select the 'Back Up Now' item from the 'Time Machine' icon in the menu bar or right-click the 'Time Machine' icon in the Dock and select 'Back Up Now' from the pop-up menu. If you don't have the Time Machine menu bar item, you can install it by doing the following:
- Launch System Preferences by clicking the 'System Preferences' icon in the Dock, or selecting 'System Preferences' from the Apple menu.
- Select the 'Time Machine' preference pane in the System Preferences window.
- Place a check mark next to 'Show Time Machine status in the menu bar.'
- Close System Preferences.
You can also create a backup using one of many third-party applications. Once you back up your data, you're ready to continue.