Although I'd hope that the lack of releases and the updates in the issue queue would be enough, sometimes users need a really blatant message. Could the project page for this module be updated to clearly state that it is no longer maintained, and that you should not use it? With well over 2,000 modules, we should try to remove ones that are no longer active to reduce the clutter on Drupal.org.

Here's a draft text:

This module is <strong>no longer being supported</strong>. No further updates to this project will be made. The merging of PHPlist and Drupal was a poor decision and this module never completely worked right. If looking for a mailing list solution, please consider one of these other projects.

<a href="http://drupal.org/project/simplenews">Simplenews</a>
<a href="http://drupal.org/project/mailman_manager">Mailman Manager</a>
<a href="http://drupal.org/project/og">Organic groups</a>

It'd also be great to close the issue queue, remove all taxonomy terms from the project, and unpublish all the handbook pages from http://drupal.org/handbook/modules/massmailer.