The default Subscriber creation policy generates an NT Logon Name (also known as the sAMAccountName and the Pre-Windows 2000 Logon Name) based on the relative distinguished name (RDN) of the account in the Identity Vault. The NT Logon name uses a subset of the ASCII character set. The default policy strips any character outside of the valid range before creating an object in Active Directory.
If the policy doesn’t satisfy the business rules of your company, you can change the policy after import. Businesses that use Identity Vault account names outside of the traditional ASCII character set should pay particular attention to this policy.