Auto Forward mails to gmail from Outlook

"Basically, with outlook and exchange you by default set up server rules. This means that the rules are applied on the server and on reception of an email regardless of whether your client (outlook) is running. With exchange it is possible to block the automatic forwarding of emails to external adresses (and it seems that your system administrators have done so). The reason it works for manual forwarding is that this is a very different process. It happens on the client, and for the server it looks like just sending any other email.

The reason for such configuration of the server is generally to prevent corporate information and secrets to be leaked out. As this is a valid concern, you probably won't have luck convincing your admins to let you forward your emails to gmail."

I don't know what you mean by auto forwarding rule, but have you added it as a normal filter / rule in your email filtering? There is an option there to forward or forward as attachment.