Removing an email account from Outlook doesn't deactivate the email account, though it will prevent you from being able to email from that account using Outlook.
From the main Outlook window, select File in the upper left corner of the screen.
Note: For Outlook 2007, select Tools > Account Settings and skip to step 3.Select Account Settings > Account Settings.
Select the account you want to delete, then select Remove.
You'll see a message warning you that all offline cached content for this account will be deleted. This only affects content downloaded and stored on your computer.
Select Yes to confirm.