How do I get around Exchange Migrator's feature to skip existing target accounts if the 'Custom Attr (NETIQKB3813)

goal
How do I get around Exchange Migrator's feature to skip existing target accounts if the 'Custom Attribute 10' field is already populated?

fact
Exchange Migrator 1.x

fact
Exchange Migrator 2.x

cause

The following NetiQ KB Article explains that the 'Custom Attribute 10' field  is used by Exchange Migrator the same way that the Microsoft Active Directory Connector (ADC) uses it. 

• https://www.netiq.com/kb/esupport/consumer/esupport.asp?id=NETIQKB1334 

In short, if the 'Custom Attribute 10' field is populated for an existing target account, Exchange Migrator will not merge on that existing target account.  Exchange Migrator will create another object with the same display name, but a different directory name.

fix
One possible workaround: 

1. Migrate with SID History during the Domain Migration Administrator user migration.
   
2. Use the Exchange Migrator EMCLI Dirsync with the merge method to mail-enable the accounts created by DMA.
   
3. Migrate mailboxes and do not use a merge method. This will make Exchange Migrator merge on the default merge method; the SMTP address.

Formerly known as NETIQKB3813