If you have multiple email account on you Android Device, you can set one as a default account for sending emails.
1. First, from the home screen, tap on 'Apps'
2. Then touch 'Email'
3. Then touch the 'Menu' button
4. Touch 'Settings'
5. Touch the account that you wish to become your Default account.
6. Then touch 'Default Account', ensuring that the box is ticked. The default account is now set.