Prevent local Mail Delivery | Kopano, postfix, fetchmail, ciphermail

I followed a tutorial and can successfully encrypt my mails via Ciphermail Gateway.

Postfix sends the mails out, fetchmail collects them from DomainFactory.
Installed is: , DomainController, Fetchmail, KVM, virsh-mananger and Kopano, Ciphermail Gateway is running as a virtual machine.

So far everything works fine, but I would like to disable the local delivery of Postfix itself.

My domain is the test de.
But I want Postfix to send out all mails via my smarthost and not try to deliver mails to or directly locally.
The mailboxes simply do not exist on the server, but they do exist at my provider.

I already tried to comment out ’ relaydomains, and mydestination’ etc. in the ‘’ but that did not work.

Postfix wants to deliver locally when it detects the domain.
How can I prevent this? I ALWAYS want to send via my smarthost.

Thanks for your help in advance.