How to change outgoing Email address for Workflow Manager 1.0

Hi, 

I have an installation of SharePoint 2013 Enterprise with Windows Azure Workflow Manager 1.0 on a single machine to test new features of SharePoint 2013 Workflows. 

SharePoint Server outgoing email settings are configured properly and working. If I invite a user to a site, the email is sent with the respective settings. Same if I want to send an email via a SP2010 Workflow from this server. 

Now if I start a SP 2013 Workflow which is using the Azure Workflow Server and want to sent a email, it fails and the mail is dropped to the badmail folder. 

If I look into the mail file in the badmail folder, the from address is workflow@noreply and not the from address out of the SharePoint outgoing email settings. 

Where can i change this settings? 

Regards

Christof