Does managing mailboxes between forests using split-brain DNS require a GALSync? RRS feed

  • Question

  • Here's our situation in a nutshell:

    We're in the middle of migrating from our old Windows 2000 domain to a Windows 2008 domain. The Windows 2000 domain is running an Exchange 2003 server. The Windows 2008 domain is running a Exchange 2010 server. We have a split-brain DNS configuration set up, so that all of our mail comes into our public-facing DNS name. We want users in our new domain to retain the same email addresses they had in the old domain. What is required to do this?

    More information:

    The old Windows 2000 domain and forest, let's call it clownfart.local, is the private DNS name for All of the clownfart.local users have a email address. We have a new Windows 2008 domain and forest called corp.clownfart stood up and running with a working trust to clownfart.local. We won't be able to migrate all of the users or their mailboxes from clownfart.local over to corp.clownfart at the same time. In the interim, we need to make sure that users on corp.clownfart and clownfart.local can still receive email through

    Additionally, all of our mail is filtered through a Cisco Ironport. The Ironport is effectively our Edge Transport server in Exchange parlance. 

    I've read that I need to set up a GALSync using Microsoft Forefront Identity Manager to manage how the mail will be delivered between the two servers. I'm guessing that I will have to point the Cisco Ironport at the Forefront Identity Manager server instead of the Exchange server(s) in order to facilitate mail routing. Everything I've read about GALSync seems to concern itself more with ensuring that contacts will synchronized between the two Global Address Lists in both forests, nothing about decided which Exchange mailbox mail will be delivered to. I just want to make sure setting up a GALSync is the answer before plowing ahead as I know next to nothing about Forefront Identity Manager.

    Tuesday, July 8, 2014 9:15 PM