Accidentally deleting your e-mail account in Apple Mail can cause all of your information in your in-box, outbox and notes to be permanently erased. Unless you have the Apple MobileMe service that retains the information on a server, you will need to use a data recovery program to restore your e-mail account. Limit your computer use--your chances of recovering your lost information lowers with every action, as your erased information is considered a temporary file. As new information is received, it will write over your erased information, which makes data recovery difficult.
Go to CNet.com. Click the "Downloads" tab at the top of the browser window and click the "Mac" tab. Type "data rescue" and press the "Enter" key on your computer or click the magnifying glass next to the Search bar. Click the "Data Rescue 3.0.1" link followed by clicking the "Download Now" button.
Connect your external hard drive to your computer.
Drag the "Data Rescue 3" icon to your "Applications" folder, and wait for the program to install onto your computer. Click "Go" at the top of your screen and select "Applications" from the drop-down menu. Double-click "Data Rescue 3" to run the program.
Click "Open" on the dialogue box. Click the "Agree" button, and click "Yes" or "No" to add the program to your dock. Click the "Demo" button if you have not purchased a license, and click "OK" to continue.
Type in your system administrator password and click "OK." Select the hard drive you wish to restore and click "Next." Click the "Deleted Files Scan" option and click the "Start" button.
Choose a new workspace location. A warning will appear stating that your workspace location is on the same drive as the Internal Boot Drive. Click "OK" and click your external hard drive on the sidebar, followed by clicking the "Open" button.
Wait for the drive scan to complete. Depending on the size of your drive, the scan can take an hour or longer to complete. Check the box next to "Mail" and click the "Recover" button to restore your deleted account and e-mails.