I want to send as user@gmail.com in my user@mydomain.com Google Apps for Business account.
Whenever I try to Add another email address you own under accounts in my Google Apps account, I get the following error:
You must send through gmail.com SMTP servers when you send as user@gmail.com. However, this functionality is not available for your account. Please contact your domain administrator for more information.
I have Super Admin access to the Google Apps (I'm the only user) and I already set Outgoing SMTP Server in the Advanced Gmail Settings but it still doesn't work.
Best Answer
Make sure the Allow per-user outbound gateways option is selected. You can find it in your Google Apps Control Panel (admin.google.com) → Google Apps → Gmail → Advanced Settings → "End User Access" section.