Email auto acknowledgement on ticket creation

Hi Expert,

We have B2C support service set up, in which ticket will be created for incoming email. For each new ticket created, email should be sent to the agent responsible for the ticket and customer (contact or individual account for the ticket).  

We are reusing the workflow rule "External.Ticket Created". like the following screenshot.

So, the ticket is created for incoming email and email notification is sent to the agent responsible. However, the customer acknowledgement email does not get sent. Any idea?

Thanks.

cheers,

julius