Contact modules

Hi all,
I must create a contact module, for a site, a little particular: the site propose services that are assigned to professionals chosen by the site administrator.
It would have to work this way: the customer write on a site and an email arrive to the administrator; he decides which professional assign the work to ( and send him the contact).
From that moment the professional and customer comunicates only by the site and on the site must stay the archive of the emails
that they exchange (visible to the administrator).
What I would like is that the professional and the customer comunicate only by the mail to the site, no need to use username and password: it must be the site that manages coded mailboxes that are assigned to them but they don't have to be in contact in others ways and don't have to ask anything else to the customer.
Does anyone of you know if there is a cms or script already ready or similar to this that I can modifiy?
Thank you for your suggestions

I know this might be a little different but you could use kayako (support desk) in that way.

As you, the admin get an email or form you can then assign it to a person. Then that person can work with the end customer back and forth via the helpdesk. It will log all emails back and forth and you could have a record of that thread.

It is not 100% what you might be looking for.. but it is done and is kept updated.

We use that system for our support and know it pretty well. If you have any questions drop me a note. The software is at kayako.com

I go to see.
Meanwhile thanks.
Bye