We would like to have some sort of mailing list functionality with groups.
The simplest way would be to add a tab to "Groups", where you can specify an IMAP account. Any new mail in the Inbox will be forwarded to the group members (similar to the ticket system, where mails are fetched from the helpdesk e-mail address). This way, you also have an archive of the conversation of that group (and any group member could get the right to see the IMAP account in the E-Mail accounts list).
I know that you can send mails to groups in the web interface, but our sysadmins and some partners prefer to send mails using their preferred mail client
und do not like to switch to the GroupOffice Web Interface everytime.