Proxies verifiedimportant

The engine binds locally, connects to the named relay, and the mail leaves carrying an address from the relay's public range. The form holds the address or range, the protocol (nat or proxy), the host and port to connect through, an optional explicit bind address, and whether the record applies cluster-wide. This is MailerQ's own version of what our proxy gate does for PowerMTA, and the comparison is worth making before we build anything: if the engine can reach rented addresses natively, the gate may be needed only for engines that cannot.