I ran into an issue where my Windows Server 2008 SMTP Service wasn't logging. Here is what I found how to resolve it.
http://weblogs.asp.net/steveschofield/archive/2008/02/29/windows-server-2008-smtp-service-logging-tip.aspx
Steve Schofield
Windows Server MVP - IIS
http://weblogs.asp.net/steveschofield
http://www.IISLogs.com
Log archival solution
Install, Configure, Forget