Message flow between Exchange 2003 and 2007 (migration process)


I'm working on migrating a companys Exchange 2003 to an Exchange 2007 SP3 server (installed on W2K8R2). I'm using this guide to help me along

I've run in to this weird issue that I'll try to explain below.

Exchange 2007 installed fine (after SP3 was released) and I could create users and mailboxes on it. Mail flow worked like a charm between the two servers both internally and externally. the installation is at the moment pretty default, although there is an anti-spam 3rd party provider configured who recieves all email for the company and then forwards it to the Exchange 2003 server. There is no smarthost or external scanner configured for outgoing email (at least not by default). The company has a German office who sends as and the default user sends email as (Danish company).

So this is what happened. A week or so after the initial installation and tests the German users (who send as started recieving delay messages and finally delivery errors on about half of their external emails. All users mailboxes are still located on the old 2003 server. So I went in and configured a smarthost so that all external email was send through this smarthost, I configured it on both the old 2003 and the new 2007 server. The problems the German users had went away then. But then another problem occured, the comunication from Exchange 2003 to Exchange 2007 went down (to be precise it was replication of public folders and delivery of emails to a test user located on the Exchange 2007 server that went down). I could see the queue just held the messages as they could not be delivered to the smarthost who obviously didn't know what to do with them. So I had to remove the smarthost and then the mailflow (smtp) started working again, but the Germans started getting errors again. So now I'm back with the smarthost and have put the project on hold as I can't perform any testing before this problem is resolved.

I've confirmed that SPF records are configured correct for the two domains, the only thing missing is a PTR record for the Exchange 2007 server.... are Germans really using PTR??

So my question is this (hence the title of the post).
Users with mailboxes on the Exchange 2003 server, does their mail flow through the Exchange 2007 server when sent? (it seems to me that the above problems point to this)

On a broader scale, could anyone please explain the mailflow when you've got an Exchange 2003 and an Exchange 2007 server installed and mailboxes created on both server (both internal and external mail). I would have thought that they minded their own business and just passed internal messages to each other ....but I might be wrong.


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when you configure your smtp virtual server to use a smart host you break communication with exchange 2007
exchange 2003 will always attempt to deliver messages over smtp using the smart host
mailflow with Exchange 2003 and 2007 can be looked at as two distinct destinations
while the message is within 2007 it will utilize Active Directory sites to determine the destination. if it is determined that the destination will be within the 2003 realm, then it determines the best route to a routing group connector

exchange 2003 will use its link state information to determine the best route. if it is determined that the destination will be within the 2007 realm, it will determine the best route to a routing group connector.

if you have multiple routing group connectors you must disable link state on the 2003 servers. failure to do so could result in routing loops.

you also have to be aware of the following:
Exchange 2007 may route a message to an Exchange 2003 connector that does not allow connections from the sending user.
Exchange 2007 does not assign message priority and will bypass any priority restrictions set on an Exchange 2003 SMTP connector.
Exchange 2007 does not assign message type and will bypass any message type restrictions set on an Exchange 2003 SMTP connector.
Exchange 2003 and Exchange 2007 define connector scope differently. An Exchange 2003 connector can be scoped to only allow servers within the same routing group to use the connector. An Exchange 2007 connector can be scoped to only allow servers within the same Active Directory site to use the connector. Exchange 2003 will recognize all scoped connectors in other routing groups as out of scope, including any scoped connectors in the Exchange 2007 routing group. Exchange 2007 will recognize all scoped Exchange 2003 connectors and scoped Exchange 2007 connectors in other Active Directory sites as out of scope. Messages are not routed to connectors that are recognized as being out of scope.
Message size restrictions set on either server version will be applied to all messages that are routed through the connector.
Exchange 2003 does not recognize this setting and will continue to route to an Exchange 2007 connector that is disabled.

perspektivaAuthor Commented:
Hi again.

Thanks for the info. I must admit that I get a bit lost reading all the "be awares", so maybe I should just ask for a solution to my problem.

How can I make sure that all external email communication from mailbox users on both servers are send to a smarthost while not breaking the communication between the two servers?

As it is now, I've installed Exhange 2007 with the default settings. There were no SMTP connectors configured on the Exchange 2003 server before the Exchange 2007 server was installed. Now there is a connector that takes care of the communication between the two servers.

When a smarthost is configured on the "Send connector" on the Exchange 2007 server and on the "Default SMTP Virtual Server" on the Exchange 2003 server, communication between the two servers goes down. This goes for mail delivery and public folder replication between the two servers.

I need to use the smarthost to avoid being blacklisted on account of a missing SPF or PTR record.

So how do I configure this scenario?

Hope for a guiding hand here :)


Making Bulk Changes to Active Directory

Watch this video to see how easy it is to make mass changes to Active Directory from an external text file without using complicated scripts.

it is the smart host on the smtp virtual server (2003)
you'll want to remove any smtp connectors in the 2003 routing group
then mail flow from a 2003 mailbox will go from your 2003 server thru the routing group connector into exchange 2007 and out

by having the smart host on the 2003 smtp virtual server all smtp traffic goes to the smart host, it won't go to exchange 2007
perspektivaAuthor Commented:
Hi again and thanks for helping out.

I'm a little concerned about deleting the connector "CPH-EXCH01-CPH-EXCH02" from the "First Routing Group". Won't deleting that break the communication between CPH-EXCH01 and CPH-EXCH02 - both mail and public folder replication?

As I see it (and please bear with me 'cause this is the first time I try this), the Exchange 2007 installation created two Connectors. One that takes care of all communication from Exchange2007 and to Exchange 2003 and one that does the opposite (from Exchange 2003 to Exchange 2007). If these are removed the servers can not communicate.... am I right or wrong?

I've attached a bunch of screendumps to help me explain the configuration. Everything is pretty standard, except for the configured smarthost that I had to set up afterwards for antispam purpose (some servers blacklisted the Exchange 2007 after a while). The SMTP connector you see is created by me to make external email from Exchange 2007 available, and the smarthost was configured on that too after a while when the spam messages started comming in.

So after all of this explanation, is deleting the CPH-EXCH01-CPH-EXCH02 connector still the solution to my problem, and will email and public folder replication from Exchange 2003 afterwards just end up at the CPH-EXCH02 server?
Thanks for your time
no, we don't want to delete the routing group connector
i am reviewing this case again to see what has been missed
On a broader scale, could anyone please explain the mailflow when you've got an Exchange 2003 and an Exchange 2007 server installed and mailboxes created on both server (both internal and external mail). I would have thought that they minded their own business and just passed internal messages to each other ....but I might be wrong.

exchange 2003 mailbox to another 2003 mailbox - in your environment the message is delivered locally (no routing needed)
exchange 2007 mailbox to another 2007 mailbox - exchange uses AD sites and services to determine the best route
exchange 2003 mailbox to 2007 mailbox - message will go from the source server of the routing group connector to a target server in the rgc, once on the target (ex 2007) it will use ad sites and services
exchange 2007 mailbox to 2003 mailbox - exchange will use ad sites to determine the best route to the routing group connector, then the 2007 source will transfer the message to your 2003 for delivery
perspektivaAuthor Commented:
wow you answer fast - thanks.

All your explanations actually made me realise that I could just put in the Exchange 2007 server as a smarthost for the Virtual SMTP Server on the Exchange 2003. so Exchange 2003 now always sends SMTP to Exchange 2007 and the Exchange 2007 sends all external email to the external smarthost. Tested it and it works. Am I missing anything serious or is this the solution to my problem?
no, that is a possible solution as long as there is a receive connector on the 2007 server that will accept the connection (which you have)
perspektivaAuthor Commented:
Yes. Many thanks for helping out here, good to know your not on your own when you run in to a problem that you can't see the start or the end of :)
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