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Exchange Internet-facing Send connectors must specify a Smart Host.

Overview

Finding IDVersionRule IDIA ControlsSeverity
V-221217EX16-ED-000160SV-221217r961101_ruleCCI-001178medium
Description
When identifying a "Smart Host" for the email environment, a logical Send connector is the preferred method. A Smart Host acts as an Internet-facing concentrator for other email servers. Appropriate hardening can be applied to the Smart Host, rather than at multiple locations throughout the enterprise. Failure to identify a Smart Host could default to each email server performing its own lookups (potentially through protective firewalls). Exchange servers should not be Internet facing and should therefore not perform any Smart Host functions. When the Exchange servers are Internet facing, they must be configured to identify the Internet-facing server that is performing the Smart Host function.
STIGDate
Microsoft Exchange 2016 Edge Transport Server Security Technical Implementation Guide2024-12-06

Related Frameworks

1 mapping across 3 frameworks
SCF0 mappings

No source states a mapping between these directly.

Also reachable in 3 hops (1) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

NET-10Domain Name Service (DNS) Resolution
0.50
NIST 800-530 mappings

No source states a mapping between these directly.

Also reachable in 2 hops (9) derived by us, not asserted by any source

Each of these is a route we composed by chaining published mappings. No publisher states a relationship between the two endpoints.

AU-10(1)Association of Identities
1.00
AU-10(2)Validate Binding of Information Producer Identity
1.00
CM-6Configuration Settings
1.00
SC-20Secure Name/Address Resolution Service (Authoritative Source)
1.00
SC-20(2)Data Origin and Integrity
1.00
SC-21Secure Name/Address Resolution Service (Recursive or Caching Resolver)
1.00
SC-23Session Authenticity
1.00
SC-8(2)Pre- and Post-transmission Handling
1.00
SI-10Information Input Validation
1.00
CCI1 mapping
CCI-001178
1.00

Details

Check Text (C-221217r961101_chk)

Review the Email Domain Security Plan (EDSP). Determine the Internet-facing connectors. Open the Exchange Management Shell and enter the following command: Get-SendConnector | Select Name, Identity, SmartHosts, DNSRoutingEnabled For each send connector, if the value of "SmartHosts" does not return the Smart Host IP Address and the value for "DNSRoutingEnabled" is not set to "False", this is a finding.

Fix Text (F-22921r411778_fix)

Open the Exchange Management Shell and enter the following command: Set-SendConnector <'IdentityName'> -SmartHosts <'IP Address of Smart Host'> -DNSRoutingEnabled $false Note: The <IdentityName> value must be in single quotes. Repeat the procedures for each send connector.