smarthost verified

Per-message routing with its own host, port and credentials. Where the node-wide smarthost turns the whole engine into a relay, this diverts one message or one campaign — which is how a customer requiring an appliance in the path can be served without changing anyone else's delivery. Two things were measured that the documentation does not mention. It must be an object — {"hostname": …, "port": …}; a host:port string is accepted into the job, silently ignored, and the message goes to the recipient's real mail server, which is the worst possible failure mode for a property whose purpose is to keep mail away from it. And the smarthost becomes the domain for throttling: the result carried headers: {domain: "127.0.0.1"} rather than the recipient's domain, so throttle rules written against the destination domain do not apply to diverted mail. Rules for smarthosted traffic have to name the smarthost.