Iis – Automatically start SMTP server in IIS

We tried going this route too, but relaying email can be quite difficult. After struggling with the Windows SMTP server for a couple months, we gave up and created an SMTP Proxy which we uploaded to CodePlex. You can use it for free and it is much simpler to use and maintain.

The IIS SMTP server is designed to either relay mail to another remote SMTP server or deliver it to a drop folder for local addresses. This means that to deliver an email to a script the script would either have to accept SMTP connections directly, retrieve the email from another server using POP (not the IIS SMTP server though, as it does not implement POP), or most likely poll the local drop folder for new messages and process them. You can configure the local drop folder for a virtual IIS SMTP server here and configure a script to monitor the directory for new files. Since the IIS SMTP server is only a virtual server you don't really have any other options. Exchange server is Microsoft's full SMTP/POP/Messaging server, which may be able to provide more email processing features.

Alternatively you could look into a different SMTP server such as the free XMail server that can be used to run external commands using custom domain processing or message filters. This however requires installing and maintaining a non-Microsoft SMTP server and using that instead of IIS SMTP.