Exchange message size restrictions must be controlled on Send connectors.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-259602	EX19-ED-000115	SV-259602r942120_rule		Medium

Description
Email system availability depends in part on best practice strategies for setting tuning configurations. For message size restrictions, multiple places exist to set or override inbound or outbound message size. Failure to control the configuration strategy can result in loss of data or system availability. This setting enables the administrator to control the maximum message size on a Send connector. Using connectors to control size limits may necessitate applying message size limitations in multiple places, with the potential of introducing conflicts and impediments in the mail flow. Changing this setting at the connector overrides the global one. Therefore, if operational needs require it, the connector value may be set lower than the global value with the rationale documented in the EDSP.

Description

Email system availability depends in part on best practice strategies for setting tuning configurations. For message size restrictions, multiple places exist to set or override inbound or outbound message size. Failure to control the configuration strategy can result in loss of data or system availability. This setting enables the administrator to control the maximum message size on a Send connector. Using connectors to control size limits may necessitate applying message size limitations in multiple places, with the potential of introducing conflicts and impediments in the mail flow. Changing this setting at the connector overrides the global one. Therefore, if operational needs require it, the connector value may be set lower than the global value with the rationale documented in the EDSP.

STIG	Date
Microsoft Exchange 2019 Edge Server Security Technical Implementation Guide	2024-01-10

Details

Check Text ( C-63341r942118_chk )
Review the Email Domain Security Plan (EDSP). Determine the maximum message send size. Open the Exchange Management Shell and enter the following command: Get-SendConnector \| Select-Object -Property Name, Identity, MaxMessageSize For each send connector, if the value of "MaxMessageSize" is not the same as the global value, this is a finding. or If "MaxMessageSize" is set to a numeric value different from the maximum message send size value documented in the EDSP, this is a finding.

Check Text ( C-63341r942118_chk )

Review the Email Domain Security Plan (EDSP).

Determine the maximum message send size.

Open the Exchange Management Shell and enter the following command:

Get-SendConnector | Select-Object -Property Name, Identity, MaxMessageSize

For each send connector, if the value of "MaxMessageSize" is not the same as the global value, this is a finding.

or

If "MaxMessageSize" is set to a numeric value different from the maximum message send size value documented in the EDSP, this is a finding.

Fix Text (F-63249r942119_fix)
Update the EDSP to reflect the maximum message send size. Open the Exchange Management Shell and enter the following command: Set-SendConnector -Identity <'IdentityName'> -MaxMessageSize Note: The value must be in quotes. or The value as identified by the EDSP that has obtained a signoff with risk acceptance. Repeat the procedure for each send connector.