STIGQter: STIG Summary: Microsoft Exchange 2019 Mailbox Server Security Technical Implementation Guide Version: 2 Release: 3 Benchmark Date: 02 Jul 2025:

The Exchange Outbound Connection Limit per Domain Count must be controlled.

DISA Rule

SV-259684r961155_rule

Vulnerability Number

V-259684

Group Title

SRG-APP-000247

Rule Version

EX19-MB-000131

Severity

CAT III

CCI(s)

• CCI-001095 - Manage capacity, bandwidth, or other redundancy to limit the effects of information flooding types of denial of service attacks.

Weight

10

Fix Recommendation

Update the EDSP to specify the "MaxPerDomainOutboundConnection" value or verify that this information is documented by the organization.

Open the Exchange Management Shell and enter the following command:

Set-TransportService -Identity <'IdentityName'> -MaxPerDomainOutboundConnections 20

Note: The <IdentityName> value must be in quotes.

or

Enter the value as identified by the EDSP that has obtained a signoff with risk acceptance.

Check Contents

Review the Email Domain Security Plan (EDSP) or document that contains this information.

Determine the value for Maximum Outbound Domain Connections.

Open the Exchange Management Shell and enter the following command:

Get-TransportService | Select-Object -Property Name, Identity, MaxPerDomainOutboundConnections

If the value of "MaxPerDomainOutboundConnections" is not set to "20", this is a finding.

or

If "MaxPerDomainOutboundConnections" is set to a value other than "20" and has signoff and risk acceptance in the EDSP, this is not a finding.

Vulnerability Number

V-259684

Documentable

False

Rule Version

EX19-MB-000131

Severity Override Guidance

Review the Email Domain Security Plan (EDSP) or document that contains this information.

Determine the value for Maximum Outbound Domain Connections.

Open the Exchange Management Shell and enter the following command:

Get-TransportService | Select-Object -Property Name, Identity, MaxPerDomainOutboundConnections

If the value of "MaxPerDomainOutboundConnections" is not set to "20", this is a finding.

or

If "MaxPerDomainOutboundConnections" is set to a value other than "20" and has signoff and risk acceptance in the EDSP, this is not a finding.

Check Content Reference

M

Target Key

5580