Take a look at http://www.rackspace.com/apps/email_hosting/rackspace_email/ http://www.rackspace.com/apps/email_hosting/rackspace_email/ . I have a client I do

Take a look at http://www.rackspace.com/apps/email_hosting/rackspace_email/ http://www.rackspace.com/apps/email_hosting/rackspace_email/ . I have a client I do freelancing for on there and they have great support and a pretty good control panel for both you and your users. Ability to do a hybrid setup with IMAP and Exchange under the same domain.