Was discussing cross forest mailbox move operations with a customer last week to review the details around network requirements for remote move requests. This is as opposed to a local move request which is used within the same Exchange Organisation.
Relevant TechNet documentation:
Create a Remote Move Request That has Exchange 2010 in Both Forests
Create a Remote Legacy Move Request Where One of the Forests Doesn't Have Exchange 2010
Prepare Mailboxes for Cross-Forest Move Requests
Prepare Mailboxes for Cross-Forest Moves Using the Prepare-MoveRequest.ps1 script in the Shell
Prepare Mailboxes for Cross-Forest Moves Using Sample Code
Start the MRSProxy Service on a Remote Client Access Server
Note that the method to enable MRS proxy has changed in Exchange 2010 SP2 as mentioned in my previous post and in the above TechNet documentation.
In addition to the above, Nagesh Mahadev also posted a great write up onto the Exchange Team Blog. My favourite section being the network requirements which has a table of the ports required for move request to function:
Mailbox Replication Service uses to communicate
RPC End Point
1024 > (TCP)
if mailbox store is not statically configured then 1024 higher ports need to be open
Microsoft-DS Service (File sharing)
Mailbox Replication Proxy service uses port 443 to communicate with other Exchange 2010 client access server via HTTPS.
Note that name resolution is required between the forests.
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