Your search for "compatibility" returned 3 results:
DONE Windows Server 2008 R2 IIS SMTP Support
Add support for using ORF with the Internet Information Services (IIS) SMTP Service on Windows Server 2008 R2, instead of just Exchange 2007/2010.
DONE Windows Server 2008 IIS SMTP Support
ORF currently does not work with the Internet Information Services (IIS) SMTP Service on Windows Server 2008.
Add support to the above platform, like in the case of Windows 2000/2003.