Exchange internal Receive connectors must require encryption.

From Microsoft Exchange 2016 Mailbox Server Security Technical Implementation Guide

Associated with: CCI-001184

SV-95375r1_rule Exchange internal Receive connectors must require encryption.

Vulnerability discussion

The Simple Mail Transfer Protocol (SMTP) Receive connector is used by Exchange to send and receive messages from server to server using SMTP protocol. This setting controls the encryption strength used for client connections to the SMTP Receive connector. With this feature enabled, only clients capable of supporting secure communications will be able to send mail using this SMTP server. Where secure channels are required, encryption can also be selected. 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 the client to the server adds protection by encrypting the sender and recipient information that cannot be encrypted by the sender.Individually, channel security and encryption have been 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 the client and server.

Check content

Open the Exchange Management Shell and enter the following command: Get-ReceiveConnector | Select Name, Identity, AuthMechanism For each Receive connector, if the value of "AuthMechanism" is not set to "Tls", this is a finding.

Fix text

Open the Exchange Management Shell and enter the following command: Set-ReceiveConnector -Identity <'IdentityName'> -AuthMechanism 'Tls' Note: The value must be in single quotes. Repeat the procedures for each Receive connector.

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