Global inbound message size must be controlled.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-33624	Exch-2-011	SV-44044r1_rule	ECSC-1	Low

Description
Email system availability depends in part on best practices strategies for setting tuning configurations. Message size limits should be set to 10 megabytes at most, but often are smaller, depending on the organization. The key point in message size is that it should be set globally, and it should not be set to ‘unlimited’. Selecting ‘unlimited’ on either field is likely to result in abuse and can contribute to excessive server disk space consumption. Message size limits may also be applied on SMTP connectors, Public Folders, and on the user account under AD. Changes at these lower levels are discouraged, as the single global setting is usually sufficient. This practice prevents conflicts that could impact availability and it simplifies server administration.

Description

Email system availability depends in part on best practices strategies for setting tuning configurations. Message size limits should be set to 10 megabytes at most, but often are smaller, depending on the organization. The key point in message size is that it should be set globally, and it should not be set to ‘unlimited’. Selecting ‘unlimited’ on either field is likely to result in abuse and can contribute to excessive server disk space consumption. Message size limits may also be applied on SMTP connectors, Public Folders, and on the user account under AD. Changes at these lower levels are discouraged, as the single global setting is usually sufficient. This practice prevents conflicts that could impact availability and it simplifies server administration.

STIG	Date
Exchange 2010 Hub Transport Server STIG	2013-09-30

Details

Check Text ( C-41731r1_chk )
Obtain the Email Domain Security Plan (EDSP) and locate the global maximum message receive size. Open the Exchange Management Shell and enter the following command: Get-TransportConfig \| Select Identity, MaxReceiveSize If the value of 'MaxReceiveSize' is set to 10MB, this is not a finding. If the value of 'MaxReceiveSize' is set to an alternate value, and has signoff and risk acceptance in the EDSP, this is not a finding. If the value of 'MaxReceiveSize' is set to “Unlimited”, this is a finding.

Check Text ( C-41731r1_chk )

Obtain the Email Domain Security Plan (EDSP) and locate the global maximum message receive size.

Open the Exchange Management Shell and enter the following command:
Get-TransportConfig | Select Identity, MaxReceiveSize

If the value of 'MaxReceiveSize' is set to 10MB, this is not a finding.

If the value of 'MaxReceiveSize' is set to an alternate value, and has signoff and risk acceptance in the EDSP, this is not a finding.

If the value of 'MaxReceiveSize' is set to “Unlimited”, this is a finding.

Fix Text (F-37516r1_fix)
Open the Exchange Management Shell and enter the following command: Set-TransportConfig -MaxReceiveSize 10MB If an alternate value is desired, obtain signoff with risk acceptance and document in the EDSP.