Write some software

I need you to develop some software for me. I would like this software to be developed for Linux . I have a debian 7 server with Plesk. I want to setup email, calendar and contacts server, so I can sync my emails, conatct and calendar similar to exchange (or gmail, outlook etc.) Ideally, I want to be able to add new domains and users to the 'exchange' environment, so that user1@[login to view URL] and user2@[login to view URL] can sync their respectiv emails, contacts and calendars. Not required but nice to have would be, that user 1&2 can share their calendars.