The relay connection only had `secure`, so with `secure: false` nodemailer
still upgraded to STARTTLS whenever the server advertised it, and there was
no way to talk cleartext to such a server. Pass nodemailer's `ignoreTLS`
through as `ignoreTLS` on the relay config, wired to
--outgoing-ignore-tls / MAILDEV_OUTGOING_IGNORE_TLS / `outgoingIgnoreTls`.
