Remote mailbox move (a.k.a. cross-forest mailbox move) refers to the process of migrating an Exchange mailbox from one Active Directory forest to another. Exchange 2010 supports remote mailbox moves via the MoveRequest cmdlets. Here are some of the considerations for performing remote mailbox moves on mailboxes which are enabled for Unified Messaging (UM). This article assumes that readers are familiar with Unified Messaging and how remote mailbox move operates in general.
Prior to Exchange 2010 SP1, if you want to perform remote mailbox move on a UM-enabled mailbox, you need to do the following:
In addition, you need to update the telephony configuration for the corresponding phone set so that all phone calls for the mailbox owner are correctly covered by the telephony system to the UM servers in the target forest.
This process poses several pain points, most importantly:
In Exchange 2010 SP1, we've extended the MoveRequest cmdlets to alleviate these pain points by removing the need for an admin to UM-disable/re-enable the mailbox and reduce voice mail downtime.
For this to work correctly, you need to "map" the UMMailboxPolicy objects in the source forest to the UMMailboxPolicy objects in the target forest. This is achieved by stamping the name of the UMMailboxPolicy object in the source forest on the SourceForestPolicyNames attribute on the UMMailboxPolicy object in the target forest. Here's an example to explain what I mean:
Set-UMMailboxPolicy -identity "Policy B" -SourceForestPolicyNames "Policy A"
Once the migration process completes, voice mail outage begins. This is because your telephony system is still sending calls to the UM servers in the source forest. Voice Mail outage continues until the telephony configuration for the corresponding phone set is updated to cover calls to the UM servers in the target forest.
If you want to reduce the amount of downtime even further, this is what you can do:
As the mailbox move finalizes, the mailbox in the source forest is deleted and the mailbox in the target forest becomes functional. If you update your telephony configuration as the mailbox move finalizes, you can reduce the window of voice mail outage. Note that this method can be cumbersome since it requires precise coordination between your Exchange admin and your telephony admin.
The SourceForestPolicyNames attribute on the UMMailboxPolicy object is part of Exchange 2010 SP1 schema. It bears the following characteristics:
Warning: User 'John Doe' can't be enabled for Unified Messaging in the target forest for the following reason: Extension 12345 is already assigned to another user on dialplan DP1 or an equivalent dial plan. Please fix the problem and enable the user for Unified Messaging manually.
An example of how this can happen is that the UM extension assigned to the mailbox was available in the target forest when the UM-specific validation occurred but is no longer so right when the move finalizes.
Chun Yong Chua