Buyer-Seller Emailing System

I am looking for a Buyer Seller Emailing System (something like Amazon). Below is the example of how it should work: Seller's real email id- seller@[login to view URL], Seller's encrypted email id- sel+2qwd2f@[login to view URL] Buyer's real email id- buyer@[login to view URL], Buyer's encrypted email id- buy+herwd4x@[login to view URL] 1. Buyer & Seller should be able to communicate to each other without exposing their real email addresses. 2. When Seller sends email to Buyer's encrypted id- buy+herwd4x@[login to view URL], email should be received in Buyer's real id- buyer@[login to view URL] + email id in From & Reply-To header should be Seller's encrypted id- sel+2qwd2f@[login to view URL] 3. When Buyer replies to Seller's encrypted id- sel+2qwd2f@[login to view URL], email should be received in Seller's real email id- seller@[login to view URL] + email id in From & Reply-To header should be Buyer's encrypted id- buy+herwd4x@[login to view URL] 4. All attachments should be taken care. 5. There should also be a way to log the email communication. May be BCC or data insertion in Joomla website database. Communication should be smooth & I would appreciate if anyone could provide me a readymade system. If not, this would be a custom development. Your proposal should contain a detailed information about how you can help achieve it.