You can rename an account, change the account name and other general information. The renamed account keeps the same ID as the original account. All messages, contacts, folders, calendar, etc. remain the same.
To rename accounts:
Go to Manage > Accounts.
In the Content pane, select the account to rename and in the gear icon select Edit.
Change the account name and other information if necessary.
Click Save. The new account name is displayed in the Account list.