Exchange 2010 mail queuing when new server is added

Up until recently, I had one Exchange 2010 server running the mailbox, client access, and hub transport roles. There was one send connector for the * address space that forwarded all mail to our hosted relay service.

Today, I added an additional Exchange 2010 server that also hosted the mailbox, client access, and hub transport roles. I did NOT add it to the existing send connector, so it was not listed as the source server in any send connector. Since I had just set it up today,(ran setup, installed the latest patches, and that's it) it did not have any mailboxes on it.

After a few hours, I noticed that mail destined for the internet was queuing up on this new server in the queue called "SMTP Relay in Active Directory Site". This new server did not have the ability to send mail to the Internet since the firewall blocked it (by design, I don't want it sending mail to the Internet).

My question is: why was the existing server trying to route outbound mail through the new server? My understanding of the Exchange routing is that if the mailbox role on the old server wants to send mail, it will always contact the hub transport role on that same server. According to http://technet.microsoft.com/en-us/library/aa998825.aspx: "If the local Mailbox server is also running the Hub Transport server role and it is not participating in a database availability group (DAG), the local server is notified. If the local Microsoft Exchange Transport service isn't running or the local Hub Transport server can't process new mail submissions because of back pressure, another available Hub Transport server is notified."

I know the hub transport role worked fine on the old server because it had been sending mail without any issues up until I installed the new server.
I will be setting up additional servers and want to understand why this is happening and how to avoid it.

Thanks!

LVL 12
Julian123Asked:
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jrhelgesonCommented:
I gather that with this new server you also installed the transport server roles?
I also assume that these servers are both in the same domain?

If so, my understanding is that the servers are trying to determine if they are running in active/passive mode, or load-sharing mode - this awareness of each other is brought about by means of Active Directory.

If both exchange servers are installed as Hub + CAS (Client Access Server), then that can only be done on a single domain by load balancing them.

The links below are for Exchange 2007, but the architecture is the same for both 2007 and 2010.

To load balance the Hubs only follow this guide:
http://www.msexchange.org/articles_tutorials/exchange-server-2007/planning-architecture/load-balancing-exchange-2007-sp1-hub-transport-servers-windows-network-load-balancing-technology-part1.html
http://www.msexchange.org/articles_tutorials/exchange-server-2007/planning-architecture/load-balancing-exchange-2007-sp1-hub-transport-servers-windows-network-load-balancing-technology-part2.html

To load balance the CASs' follow this guide:
http://www.msexchange.org/articles_tutorials/exchange-server-2007/high-availability-recovery/load-balancing-exchange-2007-client-access-servers-windows-network-technology-part1.html
http://www.msexchange.org/articles_tutorials/exchange-server-2007/high-availability-recovery/load-balancing-exchange-2007-client-access-servers-windows-network-technology-part2.html
http://www.msexchange.org/articles_tutorials/exchange-server-2007/high-availability-recovery/load-balancing-exchange-2007-client-access-servers-windows-network-technology-part3.html

To load balance the Hub-Cas Roles follow this:
http://exchangeserverinfo.com/2008/03/20/network-load-balance-for-hub--cas--exchange-2007.aspx
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Julian123Author Commented:
Thank you for your feedback, but unfortunately those links don't really answer my question. Could you please clarify?

I'm not trying to load balance hubs or CAS servers.

Thanks again for your help.
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RadweldCommented:
Hub transports in exchange 2010 perform some basic load balancing for transport servers in the same site. If you don't want the new server to send mail then simply disable its send connector. However if you have the server why not get the benefit of it?
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Julian123Author Commented:
As I mentioned above, the new server was not listed in any send connector. Why would mail be routed through it?
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RadweldCommented:
Because exchange uses active directory to route mail internally, obviously it thinks this sever is a better route, check the costs of send connector or just disable it as I suggested. Problem solved.
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Julian123Author Commented:
I don't understand your answer. This server is not listed as a source server in any send connector. Why would the other server (that is listed as a source of a send connector with the address space *) route internet mail through it?

I ask because I need to set up something similar for other customers and want to understand the behavior so I don't see issues like this again.
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RadweldCommented:
Ok have a read of this to understand how routing works for Exchange 2010

http://technet.microsoft.com/en-us/library/aa998825.aspx

By default, all Send connectors that you create can be used by all the Hub Transport servers in your Exchange organization. However, you can limit the scope of any Send connector so that it can be used only by other Hub Transport servers that exist in the same Active Directory site. To limit the scope of this Send connector, select Scoped send connector.
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Julian123Author Commented:
Thanks, but connector scoping is for something else. Enabling scoping on the connector would prevent servers from other sites from using this hub transport server. In this case, both the old and new servers are in the same site so that would have no effect.
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RadweldCommented:
Thinking about it, i'm pretty sure this is by design. I think your only option here would be to remove the hub transport role or open the firewall and gain the benefit of two servers.
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jrhelgesonCommented:
You cannot have multiple hub roles installed in a single AD domain unless they are configured for load balancing or fail-over.  Active Directory is aware of both exchange servers, even if the exchange servers themselves are not aware of each other.

You need to either finish configuring the fail-over, or load balancing (links provided above), or you need to get rid of the Hub Roles.

It keeps 'breaking' because you're not finishing your configuration.

What is the end result that you are trying to accomplish?
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Julian123Author Commented:
Mainly it's this: I have an existing server that's not in a DAG and am adding 2 new servers that will become a DAG and the old server will go away (only 1 of the two has been added so far). I'm an installer so I do this a lot. I want the new servers to not take any active role such as routing mail, etc. until they are tested, configured, have failover testing done, antivirus, etc. They will eventually be load balanced, I just don't want them to do anything yet until the configuration work is done.

Make sense?
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jrhelgesonCommented:
They won't take an active role until you start putting mailboxes on them and routing traffic to them, but as soon as they appear, it is going to create problems.  It's like plugging a second router into your network - other switches will learn its mac address and get ready to send traffic to it, acknowledge its existence, etc.
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