Stalwart as Frontend to relay message for specific domain to "real" mail server [enterprise]

[HBS-Admin]

Hi folks, I am pretty impressed with Stalwart, but I have a question regarding the subject:
I want to use Stalwart as the Internet-facing frontend and "proxy" which acts as MX and relays mails to a specific (main) domain to our backend server. Other domains should be handled by Stalwart as authorizing server.
I have created the domains and I have created a samtp directory with our backend server as the source. I have created the backend server als relay target. I assume, that I customize the RCPT-Stage but I am not sure how.

[mdecimus]

Hi, you can take a look at the routing examples for ideas.