Gmail error You must send through (my domain name) SMTP servers when you send as info@(mydomain name) However, this functionality is not...

You must send through (my domain name) SMTP servers when you send as info@(mydomainname).com. However, this functionality is not available for your account. Please contact your domain administrator for more information. What setting is causing this? The forwarder I have on the account is working. Thank you!