[MM3-users] Must issue a STARTTLS command first when forwarding from old server to new server

I have a fully functioning Mailman3 server now and have setup and alias on the old server to forward mail to the new server. We have TLS enabled on the new server, but not the old server, so the new server is rejecting the mail coming through. Our IT security will not allow me to disable TLS on the new server.

Is there a way to make an exception in mailman3 to allow a specific host to send mail through without using TLS?