Mailing list with web access

My client is currently using Yahoo Groups and they want to move to their own web site and domain. They want to have a mailing list that, like Yahoo Groups, allows them to read messages from their email client *or* from their web site.

Is there anything out there that will do this?

yes sir http://leamhost.com control panel has the abality to do sir we you like momre detailed information

Members of the list would not necessarily have the same domain as the list owner, and would not have access to the control panel.

so you need multiple a primary control account for multiple users

No. These users will be from all over: arnold@yahoo.com, betsy@aol.com, fred@joeshmoe.com. We are not giving them new accounts or new email addresses. They are simply participating in a discussion list by email, but want to be able to log into our web site to read the messages there, too. We will secure the web site and keep their names in a database so they will have to log in to the site.

you can get an script to do that but you will need an host that allows such scripts on their servers