I think it would be useful if the admin of a web could list allemail addresses for this web and all addresses and accounts they are mapped to. A click on the account should then go to the mail addresses for this user (the interface as it exists now) while a click on an email address goes to the email address and allows changes that are not available in the current interface, e.g. add more users to that email address from a list. I find that the current system is not very comfortable in this respect if a web admin wants to administer the email addresses of his web and get an overview. The list you get on the User & Email tab is only a partial list.