Aim for the high end. What would a client look like that allowed you to process between 1,000 and 10,000 inbound messages a day, answering 1-10% of them, in 2-4 hours of clock time. E-Mail is not going away, but the metaphor of the inbox and folders is obsolete and needs to be rethought from the ground up. Here is one place to start: http://www.43folders.com/2008/03/12/patterns-email-conversat...

Please feel free to contact me directly if you would like to continue the conversation. I think this is one area that is overdue for a significant change in paradigm, the evidence that the current approach isn't scaling can be found in every successful blogger who can no longer find time to read and answer E-mail.