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Exchange internal Send connectors must use an authentication level.


Finding ID Version Rule ID IA Controls Severity
V-69929 EX13-EG-000335 SV-84551r1_rule Medium
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.
MS Exchange 2013 Edge Transport Server Security Technical Implementation Guide 2019-03-11


Check Text ( C-70399r1_chk )
Open the Exchange Management Shell and enter the following command:

Get-SendConnector | Select Name, Identity, TlsAuthLevel

If the value of TlsAuthLevel is not set to DomainValidation, this is a finding.
Fix Text (F-76161r1_fix)
Open the Exchange Management Shell and enter the following command:

Set-SendConnector -Identity <'IdentityName'> -TlsAuthLevel DomainValidation