Exchange internal Send connectors must require encryption.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-80603	EX16-ED-000690	SV-95313r1_rule		High

Description
The Simple Mail Transfer Protocol (SMTP) connector is used by Exchange to send and receive messages from server to server. Several controls work together to provide security between internal servers. This setting controls the encryption method used for communications between servers. With this feature enabled, only servers capable of supporting Transport Layer Security (TLS) will be able to send and receive mail within the domain. The use of secure communication prevents eavesdroppers from reading or modifying communications between mail clients and servers. While sensitive message bodies should be encrypted by the sender at the client, requiring a secure connection from server to server adds protection by encrypting the sender and recipient information that cannot be encrypted by the sender. Individually, channel security and encryption can be compromised by attackers. Used together, email becomes a more difficult target, and security is heightened. Failure to enable this feature gives eavesdroppers an opportunity to read or modify messages between servers.

Description

The Simple Mail Transfer Protocol (SMTP) connector is used by Exchange to send and receive messages from server to server. Several controls work together to provide security between internal servers. This setting controls the encryption method used for communications between servers. With this feature enabled, only servers capable of supporting Transport Layer Security (TLS) will be able to send and receive mail within the domain. The use of secure communication prevents eavesdroppers from reading or modifying communications between mail clients and servers. While sensitive message bodies should be encrypted by the sender at the client, requiring a secure connection from server to server adds protection by encrypting the sender and recipient information that cannot be encrypted by the sender. Individually, channel security and encryption can be compromised by attackers. Used together, email becomes a more difficult target, and security is heightened. Failure to enable this feature gives eavesdroppers an opportunity to read or modify messages between servers.

STIG	Date
Microsoft Exchange 2016 Edge Transport Server Security Technical Implementation Guide	2018-08-28

Details

Check Text ( C-80335r1_chk )
Open the Exchange Management Shell and enter the following command: Get-SendConnector \| Select Name, Identity, TlsDomain If the value of "TlsDomain" is not set to the value of the internal <'SMTP Domain'>, this is a finding.

Fix Text (F-87455r1_fix)
Open the Exchange Management Shell and enter the following command: Set-SendConnector -Identity <'IdentityName'> -TlsDomain <'SMTP Domain'> Note: The SMTP Domain is the internal SMTP domain within the organization.