Setting AEA (Associated External Accounts) on the resource Exchange forest when migrating account (4217700)

There are 3 different domains each in its own forest:
A - contains disabled AD accounts holding Exchange mailboxes. AEA (Associated External Accounts) are set to the corresponding users in B domain.
B - accounts domain containing AD accounts where users are logging into.
C - target domain.

B is migrated to C. Target users will need to continue using Exchange mailboxes residing in A resource domain. How can you flip AEA (Associated External Accounts) to correspond migrated accounts from the domain C.

In the above scenario ADPW (Active Directory Processing Wizard) needs to run on the resource Exchange forest A after all AD accounts from domain B are migrated to domain C. It needs to be configured with the default options. This will change AEA (Associated External Accounts) configuration on the disabled accounts from forest A to match target migrated accounts from domain C.

Note: it is important to understand that in this scenario the ADPW will simply find all existing entries (the SID of the msExchMasterAccountSid and the SID in the ntSecurityDescriptor) and will replace it with the corresponding matching SID of the target user.

Using ADPW will not set the AEA completely. ADPW can flip the SID of the msExchMasterAccountSid and can update the ntSecurityDescriptor, and EPW needs to be used to update mailbox permissions. To clarify the entire procedure please consult your PSO or Solution Architect, or ask your Account Manager to clarify this on your behalf.

This article applies to all versions of QMM (Quest Migration Manager) for AD.