A send-only email address gives you all the benefits of multiple email addresses without any of the added hassle. Enjoy conveniences such as one password and a centralized Inbox for all your emails.
Send email from an extra email address
1. Compose a new email.
2. Select your extra email address in the "From" pull-down menu.
3. Address and compose your email.
4. Click Send.
Set your default sending address
1. Click Settings 
| Click More Settings.
2. Click Writing email.
3. From the "Default sending address," select your extra email address.