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I have set up a windows 2008 R2 server to route email from Exchange 2010 using SMTP Server in IIS.

I have 3 seperate domains and would like to route each one through a different internal and external IP for (IP Reputation etc), at the minute it is only using the primary IP on the server to route email externally.

Is this at all possible using SMTP Server in IIS, or is there any other software available to do this?

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You're making this more complicated then it needs to be. 1. Use Exchange to deliver email directly via DNS. Why are you using a smarthost? 2. Set up the appropriate SPF records for the domains in question for the ip address that the server is sending email out on. – joeqwerty Oct 10 '12 at 13:57

The default Virtual SMTP Server in Exchange will handle sending directly for all valid domains. You don't even need to create seperate virtual SMTP's for this scenario.

Send directly and you'll have no problem. You can even specify a different DNS server for your SMTP to use for outbound DNS lookup from your users and other processes.

Send through the smart host, and you'll need to deal with SPF as in the other answer.

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Setup SPF records for each domain that point back to your external IP address and you will have no issues sending email out. We have it setup this way and it works fine.

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SMTP in IIS and Exchange are pretty much the same identical product under the hood. Unless you have load/resource concerns on your Exchange server you shouldn't need to use the IIS SMTP. The exception is that if you're planning on relaying mails in the six figure range at one time, then you should look at an IIS SMTP server.

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I suspect you're talking about Exchange 2003 and previous. Exchange 2007 and 2010 implement their own SMTP service that is not related to the IIS service. In addition I would take issue with your comment regarding the scalability of Exchange SMTP vs IIS SMTP - perhaps you could cite a source for this recommendation? – Chris McKeown Oct 23 '12 at 23:06
Personal experience. I rolled out a load balanced (SMTP and DNS) solution outbound only mail solution (with the help of MSFT developers and engineers) that can handle upwards of 1 million simultaneous SMTP emails being sent. Granted, if the loads are lighter than that then something like this isn't needed. – Techie Joe Oct 23 '12 at 23:12
One more note. SMTP is not an application, it's a protocol. If the products are rewritten then it would not be considered SMTP anymore but a different product. – Techie Joe Dec 11 '12 at 15:44

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