Set up your MailService account in Gmail
Click on settings button and choose 'Settings'.
In 'Settings' go to 'Accounts and Import' tab, and click on 'Add another email address you own'.
In the new window enter the name you would like to be shown as the sender and then click 'Next Step'.
On the next screen you have to enter your details with your email service provider.
Enter the verification code received from MailService.
Your new email address is set and you can start sending emails from your new address.