Right now, I'm using Mailman 2 to run mailing lists, paying $60/year for a Linux VPS to host this. The mailing list is a key part of the three-pronged communication platform I help run. The other parts are ZOHO Wiki for our website and posting/workflow services via ZOHO Creator.
It seems to me that ZOHO should add a listserv-type mailing list to the suite of online applications. This would probably have tie-ins to CRM, business, ZOHO mail, and others. A listserv would greatly enlarge the ZOHO user-base, since each subscriber would require a ZOHO account. I would expect the service to have the typical features: commands via sent email, online GUI for the list admin to manage subscribers, personalization of email (names, unsubscribe links), mass-subscription via invitations, and so on. Any bounce processing would be done behind the scenes via ZOHO's servers.
As a model, please do not look towards Google Groups, look at Mailman or ListServ.