How to use GALsync in a migration – Part 2

28 Oct

In this second part we describe how to use GALsync during an inter-org (inter-forest) migration / cross-forest migration using exchange shared name space. If a shared smtp name space is present, both organizations are responsible for the same smtp addresses.

We start with the source forest. It has a domain with different mailbox- and mail-enabled objects. The domain name is source.local, the smtp namespace is

We already added a second smtp address to all mailbox-enabled user objects. This address will be used during migration. (you can use the cost-free tool tool to bulk modify objects attribute values).



In next step we synchronize the source objects to the new target forests domain. Objects are created as contacts and placed in a special organizational untit (i.e. import). Because both Exchange organizations share their name space we use the secondary smtp proxy address as new targetaddress of the contact. This modifcation can be done automatically by GALsync (configuration of import policy). 
The contact in the target now refers to the mailbox in the source forest – so it is possible that someone in target forest can see peter in Global Address List (GAL).

Note: you must have configured a routing path in target organization that is able to route messages to



After migrating Peter’s user object and mailbox to the target, Peters source object is deleted. The appropriate target object gets an secondary smtp-address as When GALsync synchronization is run the next time, Peter’s contact in target is deleted too.


To provide messaging functionalities in both directions, GALsync now is installed in target forest too. It will be configured to synchronize Peter back to the source, so that people in source can lookup for him in GAL. Peter will be created by GALsync as contact in source referring to Peters address in target. 

Note: you must have configured a routing path in source organization that is able to route messages to



Message Routing

In Exchange 2000/ 2003 organizations you have to configure the option “This Exchange Organization is responsible for all mail delivery to this address”

In Exchange 2007/2010 you have to configure an accepted domain from type Internal relay domain.

see these great articles: 


Finally you can provide all addresses to both organizations with GALsync. So everybody is able to see all objects in Global Address List (GAL) when using Outlook, Outlook Web Access (OWA) or mobile devices. 


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