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Here is the scenario: I have 2 Exchange Server 2010 on 2 different Virtual Machines, created by and based on Hyper-V. They have IP and domain:, ; and, respectively.

The problem is, I only have 1 public IP, say . How do I configure the settings so that I can successfully receive emails using both Exchange servers?

Given that I cannot use single Exchange server for multiple domains.

-- UPDATE --

To clarify, the and mentioned above are website domains, instead of multiple Active Directory forests. Users of the two Exchange Server shares the same Active Directory. I know that ONE Exchange Server can handle multiple domains, but I would like to separate them into different Virtual Machines, for load balancing and data separation.

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up vote 2 down vote accepted

here is what I do.

  • I have an edge transport server in a VM sitting at my provider. Is it not using subscriptions, but manuarlly configured (not so hard, but requuies 5 minutes google). It works s relay for all incoming and outgoing email, and does a lot of anti spam filtering (thanks MS for that one).
  • I have forard roles to distribute incoming emails to different targets based on their domain. Basically, for a new domain I tell it to accept it, and put in a forwarding rule for it.
  • Sending email comes from trusted sources (my email servers), identified by IP address. This requires some command line magic to allow anonymous connection from them, but this is very limited (few servers only, 2 in your case).

The VM with the edge handles NOTHING else than the edge (actually it is even named smtpgateway), allowing me to isolate impact in case of abuse (tons of spam coming) - it simply has a nice CPU limit set. Plus it is also there to buffer emails (my own server is in my office connected via VPN and end user cable modem internet, so.... it may be down sometimes for an hour or two).

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I did not quite understand your setup. You mean, you only got 1 physical server with you, and all traffic incoming are forwarded to the VM with edge transport server? then, if i am not mistaken, traffic are then diverted to different VMs / physical servers? – Raptor Mar 8 '10 at 10:45
A lot more complicatd. On the hosting side, I have a number of servers, but all the virtual ones run on one physical one.... with an outside and an inside network, physicalyl separated (different cards, switches). So, there are there actually 3 hyper-v instances - edge, 2x email systems (exchange, smartermail). Company then has another exchange server, hooking up by VPN - and that is located in another place, but also running on hyper-v. – TomTom Mar 8 '10 at 11:24
I see. Thanks for your information. I might bother you further if I encounter more problems. Again, thanks a lot! – Raptor Mar 8 '10 at 12:16

You can't, you can't have both servers listen for SMTP connections on a single IP. Your best bet is to have one Exchange server handle the collection of mail, if you set it up your routing correctly then this will result in the mail ending up in the right place. If you configure both Servers to accept mail, then you can easily swap which one actually collects mail should one go down.

The other option is to setup an edge transport server, which is designed to sit on the edge of the network and handle all the receiving of mail, and pass it on to the Mailbox servers.

Edit: I may have miss read your question, but I'm not sure what you mean when you say you cannot us a single exchange server for multiple domains, do you have multiple Active Directory domains that are not in the same forest? If so then this method will not work. If you just talking about multiple email domains, then your Exchange server can handle as many domains as you want to throw at it.

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Thanks for your answer. I have added clarification in my question. I will look into Edge Transport Server. – Raptor Mar 5 '10 at 1:26

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