There is also this key, ExcludeDisabledADAccounts.
The default Enterprise Vault behavior is not to archive mailboxes associated with disabled Active Directory users.
To change this default behavior and allow Enterprise Vault to archive users disabled in Active Directory then implement the following registry key:-
Hive HKEY_LOCAL_MACHINE\SOFTWARE\KVS\Enterprise Vault\Agents (remember for 64 bit it is under the WOW6432Node entry)
Type DWORD
Name ExcludeDisabledADAccounts
Value 0
After making the above registry change restart the Enterprise Vault Admin service.