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Exchange 2003 to Exchange 2010

I have a dilemma that I'm hoping to have some of you more seasoned folks shed some light. I have 1 Exchange 2003 server and 1 Windows 2003 DC in domainA.local.com. Now my goal is to migrate about 25 users in domainA.local.com to a totally "new" Windows 2008 R2 with Exchange 2010, which is also in domainA.local.com. I did not want the old y AD in the new AD forest, so I created from scratch. In essence I have duplicated the 2003 to 2008. My challenge is I need to start moving users to the Exchange 2010 domain a few users at a time, which I want to test slowly. Which will require me to remove userA from the old domain and add them to new domain. I have an MX record with priority 10 for the 2003 server and priority 20 for the 2010 server. I ran a test, both ports open on firewall. I created a user on the exchange 2003 host called userX.domain.com, and created another user on Exchange 2010 called userY.domain.com. I send a message to userY.domain.com, If I do that mail never gets delivered to userY(20) as it sees smtp running on 10(I believe), and returns the message as “address couldn’t be found”. The problem is I need to have both mail servers running and accepting email from internet. So how can I have both mail servers accepting email that if I email comes in a does not find a recipient on the first priority server it attempts to deliver on priority 20 server? I guess I do not fully understand how this process is supposed to work. Any info that I can be directed to or replied to here would be greatly appreciated. I have been trying to figure this out for a month now.
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1 Solution
The direct answer to your question is here:

There is an easy way to configure Exchange 2010 to relay undeliverable mail directly to another third party mailserver that isn't part of your domain.


Basically you set it up this way:

- MX records point to your Exchange 2010 server
- The Accepted Domain on your Exchange 2010 server is configured as an "Internal Relay Domain" instead of an Authoritative Domain
- A custom Send connector is configured on Exchange 2010 to relay the undeliverable mail for your company's domain to your Exchange 2003 server

This is intended to be used when you have two disparate mail systems that you need to connect while you are in the middle of a migration - For example if you were migrating everyone from Google Apps -> Exchange server, and you haven't finished adding all of the users to Exchange yet, you could configure your Exchange server to relay the mail that it can't deliver to the Google Apps servers.


However, that being said, you're going about this the wrong way.

You've basically created two completely separate active directory forests, and both forests contain a single domain, which happens to be the same name.

This is messy... moving everything to a new forest means you have to redo EVERYTHING from scratch - you have to remove all your PCs from the old domain and rejoin them to the new domain, recreate all your user profiles, move all your mail manually from the old accounts to the new ones via export to PST and import from PST.

And you'll run into some headaches and conflicts because your old domain and your new domain happen to have the same name - there will be conflicts and DNS issues when computers try to access resources on your network.

There's no reason to put yourself through all of this headache - you should be bringing your new Server 2008 and Exchange 2010 servers into the SAME domain. With Microsoft servers you are SUPPOSED to have multiple servers in your domain performing the same role to provide fault tolerance - multiple DCs, multiple Exchange servers etc. You can take advantage of this by bringing your Server 2008 and Exchange 2010 servers into your domain, making them member servers, migrating everything over to them, and running the four servers simultaneously a while, and finally removing the old servers from the domain and powering them down. You don't have to destroy your whole forest to retire old servers.
delerious_nomadAuthor Commented:
Hello Frosty555,

Thank you very much for your response. I really wanted to try to start with a clean slate with the forest. But from the way it looks I may just have to go with your recommendation, as this appears to be the most pain free, and less likely to cause downtime with the environment. I am still trying to absorb and understand fully what you have suggested and possible variations.
delerious_nomadAuthor Commented:
I believe this is the cleanest safest way to go about migrating the solution to my configuration.
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