How to Change the E-Mail Settings on Your iPhone
The e-mail settings on your iPhone aren’t all permanent; you can change some of them. The iPhone lets you change four of its e-mail settings.
To hear an alert when you successfully send a message: Tap the Sound icon on the Home screen, and then turn on the Sent Mail setting. If you want to change other settings, tap the Settings button in the upper-left corner of the screen. If you’re finished setting settings, tap the Home button on the front of your iPhone.
To add a signature line, phrase, or block of text to every e-mail message you send: Tap the Settings icon on the Home screen, tap Mail, and then tap Signature. The default signature is Sent from my iPhone. You can add text before or after it, or delete it and type something else. Your signature is now affixed to the end of all your outgoing e-mail.
To have your iPhone send you a copy of every message you send: Tap the Settings icon on the Home screen, tap Mail, and then turn on the Always cc Myself setting.
To set the default e-mail account for sending e-mail from the Photos or Maps applications: Tap the Settings icon on the Home screen, tap Mail, and then tap Default Account. Tap the account you want to use as the default. Note that this setting applies only if you have more than one e-mail account on your iPhone.