New company aquisition

My company ABC just recently purchased another company XYZ.  The XYZ company is shutting down completely 100%, they still will be needing to receive emails to the XYZ email account for about three months.  Now since their main facility is no longer going to be there, and they will be closing their shop up completely.
I know I need to move their MX record from their old IP address to one of my open addresses.  

Here is a Break down of the two systems: is on an internal exchange server 2007
only 4-8 users will be staying
They have hundreds of customers that will still need to contact them due to they were a vendor.
They are located in Austin, the users will transfer to our Austin Location. has an internal exchange 2010 server which provides email to Users in Houston, Austin and various other locations.

We have lost our tier 3 exchange individual, so it was pushed upon us Tier 2 individuals to handle this.

What would be the easiest way to do this?  I have done this before but only part of the transition, and it has been almost two years so I have forgotten most of the items.
The major hang up, is that the ownership doesn't quite understand IT, and thinks this can be done in no time.  So the time limit has been accelerated drastically.
Who is Participating?
Adam FarageConnect With a Mentor Enterprise ArchCommented:
There are two ways of doing this ...

The hard way (cross forest migration: or the simplier way, which is my way :)

Ill explain my way, since it is such a small shop that you are acquiring.

First, you would setup a new accepted domain ( and make it authorative. This would be the domain of the company you are acquiring.

The second part is repointing the MX records to your current organization. The MX records should be pointed to an A record, which would go to your SmartHost or NAT to your EDGE / HUB transport server.

After this, you would then setup a new email address policy in the same format that was setup in the Exchange 2007 organization ( and use the new authorative domain for this.

Setup up the four new mailboxes in your new organization, and set the email address policy you just created for them to this.

Then export the emails from the old 2007 Exchange server and re-import them into Exchange 2010. Exchange 2007 I would recommend using Outlook to make a PST, and then use New-MailboxImportRequest to import the data from the PST to the Exchange 2010 mailbox for each user.

Setup the email clients for the users, test and it should work.

Make sense?
ttornoAuthor Commented:
Thank you, I was just over thinking it as usual.  It makes perfect sense.  
Will do, and will post back next week with the results.
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