By default, the user accounts are created in Users container.

To redirect it to Testou, use redirusr

c:\windows\system32\redirusr "ou=testou,dc=adatum,dc=com"

To redirect the default computer account creation OU:

redircmp "OU=TestOU,DC=adatum,DC=com"

By default, the distribution group location is Users container, too.

To change it,

Set-OrganizationConfig -DistributionGroupDefaultOU 'Adatum.com/TESTOU'