Another idea is to use a redundant entry like this: 10 primary.foo.com. 20 secondary.foo.com. 30 primary.foo.com.
This is how I am setting up my network. If they want to use the lowest preference that's fine with me ;) All servers have the same spam rules on them, only different is CPU power between the boxes. Frederic Tarasevicius Internet Information Services, Inc. http://www.i-is.com/
