simplenews creates open relay.

I guess no one is interested in this issue?

The problem is this module WILL get your domain/ip on RBL lists and your services will be blocked globally. I believe this is a serious issue.

Anyone else?

Is this a security issue? If yes please report privately at https://www.drupal.org/project/simplenews/report-security-issue →

https://en.wikipedia.org/wiki/Open_mail_relay states

An open mail relay is a Simple Mail Transfer Protocol (SMTP) server configured in such a way that it allows anyone on the Internet to send e-mail through it, not just mail destined to or originating from known users.

This module doesn't have any mechanism to receive emails. I don't understand how it could possibly be an open relay. Please provide steps to reproduce.