The Intersite Messaging service enables message exchanges between computers that run Windows Server sites. This service is used for mail-based replication between sites. Active Directory includes support for replication between sites through SMTP over IP transport. SMTP support is provided by the SMTP service, which is a component of IIS. Fix: (1) GPO: Computer Configuration\Windows Settings\Security Settings\System Services!Intersite Messaging (2) REG: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\IsmServ!Start