Answer
The following registry key must be created or configured when synchronizing two or more installations of GFI MailEssentials when they are part of an Exchange 2010 DAG (Database Availability Group):
- Open regedit.exe (Start > Run > type regedit.exe and press Enter)
- Navigate to the following registry key: HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\GFI\MailEssentials\AntiSpam\Config
- Locate the DWORD named SynchAgentNoClust (or create it if it does not exist)
- Set the value to 1.