Home > Exchange 2007 > Exchange Server.. Two servers in two different sites

Exchange Server.. Two servers in two different sites


The situation is you have two separate Exchange servers in two sites and they share the same public domain name.

So the question is how does the exchange server in the first site know to forward emails to the exchange server in the second site for second site user’s?

i.e., if you have user on server 1 called user1@domain.com and user on server 2 called user2@domain.com and the MX record point to server 1.

if you send mail to user1 it will arrive to his mail box but if you send to user2 it will not arrive as his mail box is not on server 1 ( the one that the MX record point to ).

So the question is how does the exchange server in the first site know to forward emails to the exchange server in the second site for second site user’s?

Here you are the solution.

Exchange Configuration

  1. You have to choose a primary site for your public name. This primary site is the one that will receive all the email. In this example, Cairo is Primary, Alex is secondary.
  2. Setup MX records for your primary domain pointing to these servers.
  3. Create a recipient policy on each server for your primary domain. Make sure that the option about exchange being responsible for all email delivery to this address is enabled. It should be the primary recipient policy.
  4. Create sub domains for each site in the DNS of each server.
    Therefore if you had two sites of
    Cairo and Alex then you would have

    • Cairo.domain.com
    • Alex.domain.com
  5. While working in the internal DNS of each server, create MX records with the external IP address of the other server.
    Therefore the
    Cairo site will have DNS zones for Alex.domain.com and in this zone will be a DNS entry for mail.Alex.domain.com. Each of those would also be set as MX records.
    These MX records do NOT appear on the Internet, but traffic will flow on them because your local machine is looking up the MX records from the location DNS.
  6. On each server, add a new additional recipient policy – but don’t make it default. This new recipient policy should match the location.
    Continuing with our example:

    • In Cairo, it would be Cairo.domain.com
    • In Alex it would be Alex.domain.com
  7. The key is that it should NOT be the default policy on any site.

The result of this should be that all users have two email addresses – the default one ending in domain.com and a secondary one that ends location.domain.com.

NOTE: It is important that your DNS is configured correctly. The server should be configured to use your active directory domain controllers for DNS – no external DNS servers should be used.
If you need to use external DNS servers for performance reasons then configure these as forwarders on the active directory DNS servers.

Adding the Remote Users

On the primary server create a mail enabled contact for all users located on the other servers. When creating the contact, initially put in the email address for its home address (Cairo.domain.com). Once created, wait a moment for recipient policy to stamp the account. You should find that the contact now has two email addresses, @domain.com and @Cairo.domain.com. Do not add local users as they will already have an email address.

Repeat on the other server.

  • Cairo will have mail enabled contacts for Alex.
  • Alex will have mail enabled contacts for Cairo.

Sanity Check

As this can cause an email loop if not configured correctly, there is a sanity check that you can make to ensure that you have it correct.
On the properties of the contact, click on the tab “Exchange General”. In the email address box, it should say SMTP then username@location.domain.com. If it says username@domain.com then it is wrong and needs to be changed.
On the email addresses tab, the default email address should be @location.domain.com

End Result – Features and Benefits

The net result of this procedure is

  • Email for your primary domain can be delivered to any server and it will be routed correctly this is useful for backup queuing of email if the other server is down.
  • Users can type in the full public email address (username@domain.com) from any site and it will be routed correctly.
  • Users from all sites will appear in the GAL.
  • You can create distribution lists on all three sites with the same membership.
  • By using mail enabled contacts the email destined for the other sites is not stored on your server – taking up no storage space on the server.
  • The sites only need an internet connection – no direct site connection required.

It can take a while to initially configure, but once done, very easy to maintain if you have limited servers.

For any inquiries Kindly don’t hesitate to contact me directly.

  1. Fabio
    July 17, 2008 at 5:26 pm

    I have a problem: my company will upgrade Exchange 5.5 to 2007. We have 2 sites interconected by an VPN-IP: Site1 => 256kbps (15 users, includes the management staff – 2 directors, 1 CEO)
    Site2 => 512kbps (70 users, manufacturing site, 400 employees, all the servers)
    My doubt: Today we have one exchange server on each site and they are connected (all mailboxes from staff of site1 are hosted by the server on site1 and the same with the other site). Do I have to mantain these structure with Exchange 2007 or can I have only one server in Site2 where we have all the IT structure and let these 15 users from site1 (including the 2 directors and CEO) use the exchange on site2 or would be bether maintain 2 servers, one in each site???
    I’m kind of lost because I asked 2 supplyers and each one recommended different scenarios, one with the 2-server scenario (said it would be slow for users on site1 to send and receive mail) and the other recommended the only one-server scenario, saying that for only 15 users is not necessary to have one server more.
    My fear is to choose the one-server scenario and after that realize that I have poor access from site1 (directors and ceo).
    Data: file with 4mb takes aprox 4 minutes to copy from site2 to site1 (direct copy, server to server).

    Can you help me?

  2. Mohamed Fawzi
    July 17, 2008 at 10:56 pm

    Dear Fabio

    I would recommend you two servers scenario.. you will need full exchange implementation in site 2 and configure it as the hub site. install Mailbox and Hub edge server ( you can install both on the same server hardware ) in site 1.

    Performance is very important factor taking into consideration future growth

  3. August 3, 2008 at 12:15 am


  4. August 8, 2008 at 10:09 am

    Quick question that seems to be comming up where I work.
    Maybe you can help considering this post…
    Well we have our mail (pop3,smtp) hosted by some other company.
    Also, we have an exchange server at our office set to accept mail of the same domain. some users have mailboxes on both the hosted mail server and exchange, some just have one on the hosted mail server ..
    problem is if we send an email to a user that has a mailbox on the hosted server, but not an exchange mailbox at our office, we get a bounce back of course.
    could something like this be setup to accomplish what we need?

  5. Mohamed Fawzi
    August 10, 2008 at 1:19 pm

    I do not think that setup will help you a lot.
    you need to create mail boxs and SMTP additional mail for those POP3 users in their AD account

  6. Jamie
    August 22, 2008 at 5:04 am

    This exactly the setup I was looking for – thanks!!

    Do you see any problem with using Postini with a solution like this?

  7. Mohamed Fawzi
    August 23, 2008 at 10:17 am

    I think it is ok

  8. sms
    September 16, 2008 at 7:31 pm

    great stuffs you’re doing out here, keep it flairing fawzi!

  9. brian
    June 18, 2009 at 7:40 pm


    I have a similar setup. 2 Exchange 2007 servers in the same domain, but at different sites, but in the same forest. Currently, there’s only a MX record for site 1, where everyone’s mailbox is located. We’d like to move site 2’s mailbox to the server at site 2, and still have them send and receive, and have their e-mail address remain the same. Any advice?

  10. Mohamed Fawzi
    June 18, 2009 at 10:47 pm

    ok.. First let’s agree that all mails will go through Site 1. About moving mailboxes to site 2 you have to move the mailboxes using normal Exchange 2007 cmd. Just click on the mailbox and choose to move it and choose Server 2 mailbox DB.

    Check this



  11. brian
    June 18, 2009 at 10:57 pm

    The moving isn’t an issue, that’s the easy part. I’m having issues once I move the mailbox sending or receiving new messages. Connectors were setup when I added the server, but I think they need to be modified. The boxes are on separate subnets, but are communicating freely, via rdp, ping, moving mailboxes, etc… Any thoughts?

  12. Mohamed Fawzi
    June 19, 2009 at 8:02 am

    I think you need hub server in the 2nd site. do u have one there?!!

    • brian
      June 19, 2009 at 5:07 pm

      Of course. The exchange servers are both hub servers…

  13. Mohamed Fawzi
    June 19, 2009 at 6:17 pm

    There are some big differences between the way that Exchange 2003 and Exchange 2007 perform message routing, and also there are some similarities. Think for a minute about why you created routing groups and routing group connectors. When you created these objects, you defined how Exchange 2003 servers communicate. Exchange 2003 servers in the same routing group can communicate directly with one another. Exchange 2003 servers in different routing groups have to use routing group connectors to communicate, and each routing group connector defines a point-to-point connection between routing groups. When no point-to-point connection between routing groups exists, SMTP traffic has to relay from routing group to routing group to get where it is going.

    In Exchange 2007, Active Directory site membership determines which Exchange 2007 servers can communicate directly with one another. Exchange 2007 Hub Transport servers use the intra-organizational Send connector (implicit and invisible!) to relay messages to other Hub Transport servers, whether they are located in the local Active Directory site or in a remote Active Directory site.

    Every time that a message leaves the confines of the routing group or Active Directory site where it originates, it must select a route to its destination. The algorithms used to determine routing paths in Exchange 2003 and Exchange 2007 are very similar. The server versions simply consider different configuration objects.

    Check this



    Currently I am in the airport, Can you please send more information about your setup?

  14. brian
    June 19, 2009 at 6:23 pm

    I read the petri article yesterday, and the sites are setup correctly, down to the subnet. Also, the connectors that were created were done automatically when I installed the second exchange 2007 server. One is in California, one is out of state. I need all mail to route through California for the time being, as the DNS work has not been setup on the remote site. I can send e-mail from within the remote site, but any email from one site to another fails, and mail bound for the internet fails as well.

  15. Mohamed Fawzi
    June 19, 2009 at 6:35 pm

    I think you need to check this

    Managing Exchange 2007 Message Routing

    What about DNS in the remote site ? Is it AD integrated or stand alone

  16. brian
    June 19, 2009 at 7:18 pm


    So I do a get-adsite, and under hubsiteenabled, I see both sites are marked as false.

    A get-adsitelink returns 100 for AD cost, and no value for Exchange… Seems like we are getting somewhere!

  17. Mohamed Fawzi
    June 19, 2009 at 11:13 pm
  18. September 10, 2009 at 9:52 pm

    Hi! I was surfing and found your blog post… nice! I love your blog. 🙂 Cheers! Sandra. R.

  19. susil khatri
    November 6, 2009 at 3:14 pm

    watch the tv shows of all dates only at


  20. A Kar
    November 7, 2009 at 9:50 pm


    We have an existing Exchange 2007 setup where 1 Exchange server available in SITE A and all Mailboxes from SITE A and SITE B resides on SITE A’s Exchange Server only. Now we want to install second EXCHANGE 2007 server in SITE B that will host Mailboxes of SITE B users.

    My questions:
    A> How to proceed?
    B> How to make sure that synchronization between SITE A & SITE B servers ?

    Thank you & hope to receive your suggestions by today please.

  21. Mohamed Fawzi
    November 9, 2009 at 10:29 am

    ok…It is easy..just install EX MBX on site B (With hub server) and AD will manage the users membership based on the site membership. Take into consideration that you can only publish one CAS from the external

  22. Sergio
    September 12, 2011 at 8:05 pm


    i am trying to couple 2 different exchange 2007 servers on 2 different sites. I followed the instructions above exactly. I seems to work until the email leaves server1, and is forwarded to server2. I get an error message from the internet provider, and it looks like this:
    “ does not like recipient.
    Remote host said: 550 5.1.1 recipient domain not found Giving up on”
    I think there is a check on the existence of the extension used in the mail address.
    Any idea how to solve this?


  23. pkou
    November 13, 2012 at 9:42 am

    very nice article. i have a situation going on here also and i was wondering if someone has something to say. i have o forest with an exchange 2003 and i want to migrate mailboxes to another forest with exchange 2003 but share the same smtp namespace. i have found this article in technet: Planning to Deploy Exchange in a Multiple Forest Environment ( http://technet.microsoft.com/en-us/library/bb124677(v=exchg.65).aspx ) but is a little bit of trouble to schedule everything by yourself, so if someone has another idea , is welcome to suggest it.

  24. February 17, 2013 at 12:31 am

    each time i used to read smaller posts which as well clear their motive, and that is also happening with this article which I am reading now.

  25. Eddy
    March 8, 2014 at 5:29 pm

    i need to ask a question:

    This setup seem just the exact setup i’m searching for. i still have to make 2 active directory right? and can users of domain A have privilege access on shared files of domain B?

    Your plan consist a good way to monitor all emails.

    Would highly appreciate your reply


  26. Eddy
    March 8, 2014 at 5:30 pm

    oh and this is applicable on exchange 2013 right?

  1. No trackbacks yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )


Connecting to %s

%d bloggers like this: