SMTP monitoring Tool

Yes, I would like almost like a relay, that sits between a clients computer and a mail server, that will scan an email for certain flags maybe bad words or something, and if the email is ok, It will allow it through, if it is set to be bad, then it terminates the email. ## Deliverables 1) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 2) Installation package that will install the software (in ready-to-run condition) on the platform(s) specified in this bid request. 3) Complete ownership and distribution copyrights to all work purchased. ## Platform Should work with most operating systems mainly Microsoft that would be handling an email server