Perform the following steps:
Choose Tools -> Settings to display the Settings dialog.
Click on the Sun Java System Accounts
button in the left pane.
Email and Calendar displays
a table of accounts that you have created, in the right pane.
Select the account that you want to delete.
Click Remove to display a confirmation alert.
Click Delete to delete the selected account.
Click OK to close the Information alert that tells you that you must restart
Email and Calendar.