I have tried all the usual mailing list apps (phplist, dada, mailman) but none do exactly what I want.  The requirements seem fairly straight-forward but I can't find an app or service that meets all of them:Paste or input a list of users (create users not send out invitations)Create and manage groups of these users as mailing lists (some users may be on multiple lists)Associate lists with an email address so any user can send an email to the whole list (must be sent to the list automatically or with a cron job) - I don't want to have to use a web interface to send emails.Needs to be able to handle HTML emails and attachmentsUnless I am missing something none of the apps I have tried can do all of this.  PHPList came the closest with the mail2list plugin but it does not work reliably and attachments fail.
PHP Mailing List Software
php;looking for a script;mailing list
This is pretty old school http://www.gnu.org/software/mailman/index.html when you are searching for mailing list software these days most assume you want to have control of a list of opt-in's to email newsletters out to and only out.NGINX uses the mailman software above integrated with their support forums http://nginx.com/support.htmlUnless i'm mistaking what you are looking for is an application to let users email one address and have it forwarded to everyone on the list. Like the old yahoo groups, and google groups?Another really old mailing list app http://www.greatcircle.com/majordomo/