To all admin / HCI / Net knowledgeable types

Do you know of a mailing list / web forum system satisfying the following requirements:

* Allows posting by both web interface or sending an email
* Gives users the choice to read through: email interface, web interface. (intermediate solutions, such as "daily digest by email" and "receive only new topics by email" are a nice plus)
?

YahooGroups is a pretty good solution, except that it has advertising. (I bet we would pay a good amount to get rid of it, but Yahoo doesn't seem to provide this option )

I am trying to organize a set of mailing lists for my institute: this is my idea