Yes, I had the email address already specified on the Web Interface page.
But then that made me think you are needing the ArGoSoftMailServerWeb service to be running. You are using a component library in ArGoSoftMailServerWeb? I have the AGS Mail Server Web service Disabled because I am hosting some websites on port 80 and 443 in IIS. I found out if I stop my IIS web server and enabled AGS Mail Server Web service, then the auto-responder works for the Dummy mailbox.
But I still need to run my IIS web server on port 80 and 443 for my websites.
I figured out a workaround:
Enable AGS Mail Server Web service on a different port, like 8080 and 4443. I did not need to open these ports on the gateway firewall (external gateway).
Then I can still use port 80 and 443 with IIS.
Archie, I'm not sure if requiring AGS Mail Server Web to be enabled is what you intended for sending auto-responder for Dummy mailbox, but this workaround works so that I can still use IIS.