Exchange receive connectors must control the number of recipients per message.
An XCCDF Rule
Description
<VulnDiscussion>Email system availability depends in part on best practice strategies for setting tuning configurations. This configuration controls the maximum number of recipients who will receive a copy of a message at one time. This tunable value is related to throughput capacity and can enable the ability to optimize message delivery. Note: There are two types of default receive connecters: "Client Servername" accepts SMTP connections from all non-MAPI clients, such as POP and IMAP. As POP and IMAP are not authorized for use in DOD, these should not be present. Their default value for MaxRecipientsPerMessage is 200. IMAP Secure is not restricted and may be configured. "Default Servername" accepts connections from other mailbox servers and any Edge Transport servers. Their default value for MaxRecipientsPerMessage is 5000.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility></Responsibility><IAControls></IAControls>
- ID
- SV-259600r942114_rule
- Severity
- Medium
- References
- Updated
Remediation - Manual Procedure
Update the EDSP to reflect the Maximum Recipients per Message value.
Open the Exchange Management Shell and enter the following command:
Set-ReceiveConnector -Identity <'IdentityName'> -MaxRecipientsPerMessage 5000