You have Exchange 2013 and above. You have added at least one IP address in the IP Allow List or IP Block List, or you have an IP Block List Provider to the Exclaimer Anti-Spam configuration, but the list is not being checked when filtering emails.
IP address filters and IP Block List Providers are added to the Connection Filtering Agent feature in Exchange Anti-Spam. In Exchange 2013 and above, this is only installed on an Edge Transport server by default. It is not installed by default when Exchange Anti-Spam is enabled on a mailbox server.
The Connection Filtering Agent can be installed manually on an Exchange 2013+ mailbox server as a FrontEnd Transport Agent, using the following PowerShell cmdlet:
Install-TransportAgent -Name "Connection Filtering Agent" -TransportService FrontEnd -TransportAgentFactory "Microsoft.Exchange.Transport.Agent.ConnectionFiltering.ConnectionFilteringAgentFactory" -AssemblyPath "C:\Program Files\Microsoft\Exchange Server\V15\TransportRoles\agents\Hygiene\Microsoft.Exchange.Transport.Agent.Hygiene.dll"
Once installed, you need to run the following command to enable the filter:
Enable-TransportAgent -TransportService FrontEnd -Identity "Connection Filtering Agent"
Once enabled, you must restart the Microsoft Exchange FrontEnd Transport service to activate the filter.
Further information can be found here.
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