How can I set up mailing lists?

We have several mailing lists set up on our current mail server, like this:

webmaster@example.com, helpdesk@example.com moss@example.com
sales@example.com jen@examle.com, tom@example.com, lisa@example.com

Moss is the IT technician, he will get emails addressed to webmaster and helpdesk. Jen, Tom and Lisa are from sales department, emails to sales@example.com will be delivered to all of them.

I am a little confused to configure CASG for this, as there is no “Mailing list” in the menu. Should I just add webmaster, helpdesk and sales as users? If so, how can I route emails to respective list members?