External Submission SMTP

[theduke]

I need to use an external SMTP server for submissions after verifying the credentials locally (auth &local_authdb).

It is not clear to me from the documentation how to do this, an example would be appreciated!

[foxcpp]

submission tls://0.0.0.0:465 tcp://0.0.0.0:587 {
    limits {
        # Up to 50 msgs/sec across any amount of SMTP connections.
        all rate 50 1s
    }

    auth &local_authdb

    source $(local_domains) {
        check {
            authorize_sender {
                prepare_email &local_rewrites
                user_to_email identity
            }
        }

        destination postmaster $(local_domains) {
            deliver_to &local_routing
        }
        default_destination {
            modify {
                dkim $(primary_domain) $(local_domains) default
            }
            # deliver_to &remote_queue     <--- this is default, put into local queue that is configured to then deliver messages directly
            deliver_to smtp tcp://whatever.submission.server.you.use:25  # <---- here is what you probably want, transparent forwarding via remote server
        }
    }
    default_source {
        reject 501 5.1.8 "Non-local sender domain"
    }
}

Here is the reference for any additional configuration you may want to do:
https://maddy.email/man/_generated_maddy-targets.5/#smtp-transparent-forwarding-module-targetsmtp
e.g. to use implicit TLS use tls:// instead of tcp://

[theduke]

Thanks!