In Exchange 2007 is it possible to route to a smarthost if you're sending from @abc.com, but to send directly to the internet if sending from @xyz.com? Or is the smarthost an all or nothing type of configuration? Ultimately we will have all domains routing through a smarthost, but this would be handy for testing purposes. To further explain the reasoning, and maybe someone can suggest a better solution, we have ~30 domains that come in to our Exchange2007 server. When the server sends mail out directly to the internet, it goes out as the single public IP attached to that server. The concern is that if, for example, a system is infected with a worm and starts spamming, it can result in our public IP being blacklisted. This would then affect all domains hosted on this server. So the solution we're currently considering is sending all domains to a smarthost, such as postfix, which will send mail out using a dedicated virtualIP for each hostname. Thanks, Matt

This cannot be done with native Exchange 2007. You can only route based on the destination domain. It should be possible to write a transport agent that accomplish this, but I havent seen anything out there check out the Exchange SDK for tips about transport agents http://msdn.microsoft.com/en-us/library/aa562613.aspx