The Exchange Recipient filter must be enabled.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-259620	SRG-APP-000261	EX19-ED-000134	SV-259620r961161_rule	2024-12-06	2

Description
Email system availability depends in part on best practice strategies for setting tuning configurations. Careful tuning reduces the risk that system or network congestion will contribute to availability impacts. Filters that govern inbound email evaluation can significantly reduce spam, phishing, and spoofed emails. Messages from blank senders, known spammers, or zero-day attack modifications must be enabled to be effective.

Description

Email system availability depends in part on best practice strategies for setting tuning configurations. Careful tuning reduces the risk that system or network congestion will contribute to availability impacts. Filters that govern inbound email evaluation can significantly reduce spam, phishing, and spoofed emails. Messages from blank senders, known spammers, or zero-day attack modifications must be enabled to be effective.

ℹ️ Check
Open the Exchange Management Shell and enter the following command: Get-RecipientFilterConfig \| Select-Object -Property Name, Enabled If the value of "Enabled" is not set to "True", this is a finding. Note: The default value is set to "True".

✔️ Fix
Open the Exchange Management Shell and enter the following command: Set-RecipientFilterConfig -Enabled $true