Development of an email forwarding website

I would like to develop an 'email forwarding' website, which would work as follows: * Users are allocated an email address on our domain * Any emails that come through to this address are forwarded to the user's preferred mail client (ie. the email address they check most frequently) * Mechanism to enable users to easily send mail using their preferred mail client, but so that it appears to be sent from our domain To do this, we are looking to build the following: * 'Sign-up' page to allocate a new user an email address on our domain * Hosted coding to handle 'email forwarding' functionality (see above description) * Simple administration tool to manage users Please contact me for further details and specifications.