Drupal's modularity means that a highly customized mailing list can be constructed from existing modules without needing a dedicated 'mailing list' module. It also means that a mailing list can be integrated with existing installs (such as with Open Atrium), or built along with a new site.
Two lists follow: one of required modules, and one of optional modules that add bells and whistles to your mailing list. Such bells and whistles include allowing posters to upload files and images attached to nodes and/or comments, adding list moderation (using Action Email Roles to notify moderators that new posts need their attention), and allowing posters to send email from more than one email address (Multiple Email Addresses module).
The setup uses Organic Groups for creation and management of mailing lists. It uses Mailhandler, Mail Comment, Feeds and Feeds Comment Processor to handle incoming emails that will be converted to nodes and comments. Finally, it uses Messaging, Notifications, HTML Mail or MIME Mail, and PHPMailer to send messages to group members/subscribers.