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If you've set up more than one email account on your phone, you can select a default email account. When you send an email message from one of your phone's applications, the default account will be used unless you're asked to select an account before sending the email message.
Press the menu icon.
Press the Menu key.
Select default email account
Press the required email account.
Press Default account to select the email account as your default account.
Return to the home screen
Press the Home key to return to the home screen.