Messages with blank sender field must be filtered.

From Exchange 2010 Edge Transport Server STIG

Associated with IA controls: ECSC-1

SV-44063r1_rule Messages with blank sender field must be filtered.

Vulnerability discussion

By performing filtering at the perimeter, up to 90% of SPAM, malware, and other undesirable messages are eliminated from the message stream rather than admitting them into the mail server environment. Anonymous email (messages with blank sender fields) cannot be replied to. Messages formatted in this way may be attempting to hide their true origin to avoid responses, or to SPAM any receiver with impunity while hiding their source of origination. Rather than spend resource and risk infection while evaluating them, it is recommended that these messages be filtered immediately upon receipt and not forwarded to end users.

Check content

Open the Exchange Management Shell and enter the following command: Get-SenderFilterConfig | Select BlankSenderBlockingEnabled If the value of 'BlankSenderBlockingEnabled' is not set to 'True', this is a finding.

Fix text

Open the Exchange Management Shell and enter the following command: Set-SenderFilterConfig -BlankSenderBlockingEnabled $true

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