Write Automatic email relay app

Our requirements are fairly simple, we are open to different ways of implimentation, however we would prefer something that intergrates with Outlook (possibly VBA?) and must run on a Windows 7 machine. We need a system that receives an email with a specified phrase in the subject line (the content of the email will be ignored). The system then needs to send a specified email (HTML with graphoics) to several different email addresses. The email sent is a generic email (not customised to each recipient) and the same email needs to be sent to multiple recipients at the same time from one email address. We will run a small Windows machine for this app that can run MS Office and Outlook 2007. Could upgrade to 2013 if absolutely required to. We can't run exchange or SQL or anything large. We are looking for someone that can come up with a cost effective solution