Plain Text Options for outbound email must be configured.

From Microsoft Outlook 2013 STIG

Part of DTOO228 - Plain Text Options

Associated with: CCI-002418

SV-53887r1_rule Plain Text Options for outbound email must be configured.

Vulnerability discussion

If outgoing mail is formatted in certain ways, for example, if attachments are encoded in UUENCODE format, attackers might manipulate the messages for their own purposes. If UUENCODE formatting is used, an attacker could manipulate the encoded attachment to bypass content filtering software.Outlook 2013 automatically wraps plain text messages and uses the standard MIME format to encode attachments in plain text messages. However, these settings can be altered to allow email to be read in plain text email programs that use a nonstandard line length or that cannot process MIME attachments.

Check content

Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Outlook Options -> Mail format -> Internet Formatting "Plain text options" is set to "Enabled" where line length is "132" and that a check does not exist in the "Encode all attachments in UUENCODE format when sending a plain text message" check box option. Procedure: Use the Windows Registry Editor to navigate to the following key: Criteria: If the value for HKCU\Software\Policies\Microsoft\Office\15.0\common\mailsettings\PlainWrapLen is REG_DWORD = 132 (decimal) and the value for HKCU\Software\Policies\Microsoft\Office\15.0\outlook\options\mail\Message Plain Format Mime is REG_DWORD = 1, this is not a finding.

Fix text

Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Outlook Options -> Mail format -> Internet Formatting "Plain text -> options" to "Enabled" where line length is "132" and that NO Check is visible in the "Encode all attachments in UUENCODE format when sending a plain text message" check box option.

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