EMAIL redirection service

Hi, I have an information system that works in the cloud as a SAAS with few ooganizations and users. I have "email like" support within my system where the users can communicate between themselves. each time a user send a message the system also send the message to his personal real email from an applicative address (like . #username#@[login to view URL]) when the receiver reply to this message the message is being sent to the system address (like . #username#@[login to view URL]). I need to develop a small service that will integrate with the SMTP server in my system. the service should read the messages and store it in my SQL DB (including all email data, attachments metadata) and will also forward/redirect the email to the recipent to his real email address which is stored in the SQL DB ( like convert #username#@[login to view URL] to #usernamerealaddress#@[login to view URL] ).