Change the "From:" Field - Hotmail

Microsoft Account Setup

The old versions of Hotmail kept separate credentials for each user. The Outlook.com service, which superseded Hotmail, is tied to a Microsoft Account.

To change the display name for your email account — using a hotmail.com or an outlook.com address — you'll need to change it for your Microsoft Account by editing your profile page.

Log in to your Microsoft Account Profile page then just click Edit name below your display name. Change your name, solve the CAPTCHA, then save. This change will propagate to all accounts (not just email) federated with your Microsoft Account.