All  --

I have a large scale Exchange Migration occuring with over 4000 users between 2 completely seperate active directory forest.  Due to the large amount of data i'd like to do a pull of all data 2 weeks prior,and then during the cutover do just a delta.  The email tool that I am using requires me to have staged on my side the proper SMTP address of the user that's migrating in.  The issue: If I stage an account on my side, and one of my internal users sends and email to that staged email address, my exchange enviornment will send it to the mailbox in my enviornment.  This is not desirable as I'd like mail flow for that domain to continue to go the clients mailbox until I take over the MX record.

So the question is, how can I have email mailboxes @whatever.com in my exchange enviornment, without intecepting internal email from @whatever.com. This is for my internal users only, I'm aware that I don't own the MX record yet so I won't be getting mail from the outside world at this address space.

I do not have this domain as an accepted domain, but i tested by adding an additional email address to my mailbox, test@whatever.com, and my Exchange enviornment still delivered me the messege. 

Running Exchange 2010 SP1.  Any help would be apprec

Hello,

In order to solve your issue as soon as possible, please make sure the following questions:

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1. Please explain what the email tool is.
2. Please make sure you migrate mailboxes across forest between exchange 2010 and exchange 2010 or between exchange 2010 and exchange 2013.
3. I dont completely understand that If I stage an account on my side, and one of my internal users sends and email to that staged email address, my exchange enviornment will send it to the mailbox in my enviornment. Do you mean when your internal users send message to that staged email address, your exchange server will prevent the message or other meanings. 

Additional article for your reference.

Exchange 2010 Cross-Forest Mailbox Moves

http://blogs.technet.com/b/exchange/archive/2010/08/10/3410619.aspx

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1)Email tool is Netmail migrator. 

2) This will be a migration from Groupwise to Exchange 2010 SP1.

3) Yes my users may need to send email to the company that will be migrating into my organization.  A limitation to the tool I'm using requires me to stage the email accounts that will be migrating (A process called mapping).  Meaning I will need to add the users and their SMTP addresses for the organization that's migrating into my exchange enviornment.  Is it possible to send mail to the organization (from my internal exchange enviornment) without the mail going into my staged accounts?

Thank you for the reply

Hello,

Do you mean the message will not go into the staged accounts when you send message from my internal exchange environment to the organization? If so, in exchange server, the recipient resolution will be processed by categorizer. If you add the users and their SMTP addresses in your environment, your message will deliveryed to the user's mailbox.