Setting the IP address that the SMTP service uses in Windows Server 2008
Solution 1:
I recommend using HMailServer instead as it is free and much better (finer SMTP controls, better logging/troubleshooting tools). You can disable the POP and IMAP functionality easily.
Anyway, you should be able to change the IIS SMTP binding per below. It looks like it is for inbound, but it may also work for outbound. If not, I think it might bind to the first IP address in Windows, so you can make the IP you want to be the outbound the primary IP on your system. HMailServer will let you select the IP to bind to though.
