So I'm setting up a SMTP gateway that sits behind my ISA box, yet in front of my Exchange Front/Backend configuration.  SMTP is gone from the IIS MMC.  I open port 25 locally fine.  The service is definitely installed and functioning.  And yet I have no way to do anything to it.  Microsoft Exchange isn't installed on here, so it hasn't hidden in the Exchange System Manager.  Fantastic.

Found this:

SYMPTOMS
After the installation of the SMTP service on Windows Server 2003, the SMTP tree may not appear in the IIS Manager console.
 
For the Windows 2000/IIS 5.0 version of this article, please see:
"IIS 5: SMTP and NNTP Virtual Server Missing in Internet Services Manager"
http://support.microsoft.com/?id=297261

RESOLUTION
Method 1: Click the "Start" button, then "Run…" and type:
regsvr32 %systemroot%\system32\inetsrv\smtpsnap.dll
Alternatively, %systemroot% can be replaced with the drive Windows Server 2003 is installed on
 
Method 2: Uninstalling and re-installing IIS including the SMTP service has also proven to fix the problem, it is, however, recommended to try method 1 first.