As mentioned above if you know your ISP smtp information you can setup a remote SMTP in IIS ..
1. In IIS click the SMTP virtual server, right-click Domains > New > click Domain.
2. Click Remote> click Next.
3. In name field type the name for your email domain > click Finish.
4. Right click this new domain entry > Properties
5. At the bottom choose option to Forward to smart host and then enter the smtp information for your ISP (See Image - same information you would use if you were POPing and needed to use ISP smtp server)
6. Point any app needing email to this iis server and you are good to go