If you are running Exchange in a mixed-mode environment, the ADC (Active Directory Connector) may not replicate information to the Exchange Server 5.5 directory and the Application event log of the ADC client may contain:
Event Type: Error
Event Source: MSADC
Event ID: 8341
Description: ADC cannot replicate to Exchange 5.5. because, on this server, LDAP Client Integrity is set to '2' (always sign.) Exchange 5.5 does not support LDAP signing. To allow this server to connect to 5.5., set the registry key registry_subkey to 0 (never sign) or 1 (sign if possible) value.
This behavior will occur if you bind to an Exchange 5.5 server running Windows 2000 SP3, or a later version of Windows, and the LdapClientIntegrity Value Name, a REG_DWORD data type, is set to 2, the default, which indicates that LDAP signing and sealing is always on, because Exchange 5.5 does NOT support LDAP signing.
The valid data values are 0, do not use signing, or 1, use signing on supported servers, but do not use signing if a signed session cannot be established.
The key where the LdapClientIntegrity Value Name must exist is HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\ldap.
NOTE: If the ldap sub-key does NOT exist, create it.