If you are using more than one account, you can specify which account is the default so that it will be the first account to be processed. Microsoft Outlook sends your messages using the default account unless you click the Accounts button (next to the Send button) on the message to choose another account to use for that message.

1. On the Tools menu, click E-mail Accounts.
2. Select View or change existing e-mail accounts, and then click Next.
3. In the list, click the e-mail account you want, and then click Set as Default.