To know how to change your mail name, open the Email application. Click the mail address pull-down list, and then you have to click Edit email addresses. Now, this will open a new menu. Next, click your name and then change it to anything that you want to keep. In Gmail, this option is cannot be changed. In this case, you have to create another Google account with another username. You will not be able to change the email address on the account to an email address that is related to the Google account.