Custom dynamic Private Messaging solution

I need a private messaging client where users of my site will be able to send messages to each other and to email addresses. The messaging module must be heavily Ajaxified (jQuery), and will have some predefined filters and labels. ## Deliverables I'm developing a very large website and have decided to outsource certain parts of my work. Right now I am in need of a private messaging "module", which I will be in charge of integrating within the site. The work must be done entirely in PHP and Javascript preferably using jQuery with a MySQL db, as thats the environment I'm developing it in. The messaging module I require is quite straightforward for someone with a good knowledge of php + js but it will be more sophisticated that other private messaging services seen elsewhere (e.g. Facebook, Myspace, PhpBB forums...) and behave more like Gmail in many aspects. Messages will be threaded in conversations, and will have predefined, not custom labels. For example, an alert message may be automatically sent to someone and it will have the "alert" label and be viewable in the alerts pane/filter along with the rest of alerts received. Messages will have to be able to be sent both to internal users and emails if entered. The fields will be as one can imagine auto-suggest, and the whole messaging client will be as ajaxy as possible. The site is being designed with an internationalisation point of view, so there should not be any hardcoded strings in the JS if possible. I'll explain how it currently works once I accept a bid. Just to state the obvious, I will be needing the typical forward, reply, delete, attach options as well as 5 different panels / views: Inbox, Sent Messages, Drafts, Trash, and Compose message. If the user hasn't got enough time to do all of it by the agreed timeframe I would prefere to take out the panels drafts and trash, as they are not as important. The styling of the application will be very simple and straightforward, quite like Gmail, but simpler in some aspects. I have designed some highly detailed mockups and will release them to the chosen programmer for guidance. The quicker you can do this the better, as I still have a lot of work to do, and I'm planning on outsourcing more in order to meet my deadline.