Plain Text Options for outbound email must be configured.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-71137	DTOO228	SV-85761r1_rule		Medium

Description
This policy setting allows you to control how plain text messages are formatted when they are sent from Outlook. If you enable this policy setting, text is automatically wrapped in Internet e-mail messages and attachments are encoded in UUENCODE format. If you disable this policy setting, Outlook uses the standard MIME format to encode attachments in plain text Outlook messages. Users will not be able to change this configuration. If you do not configure this policy setting, the behavior is the equivalent of setting the policy to Disabled, but users can modify plain text options in Outlook when required by clicking Tools, clicking Options, clicking the Mail Format tab, clicking Internet Format, and changing the values under "Plain text options".

Description

This policy setting allows you to control how plain text messages are formatted when they are sent from Outlook. If you enable this policy setting, text is automatically wrapped in Internet e-mail messages and attachments are encoded in UUENCODE format. If you disable this policy setting, Outlook uses the standard MIME format to encode attachments in plain text Outlook messages. Users will not be able to change this configuration. If you do not configure this policy setting, the behavior is the equivalent of setting the policy to Disabled, but users can modify plain text options in Outlook when required by clicking Tools, clicking Options, clicking the Mail Format tab, clicking Internet Format, and changing the values under "Plain text options".

STIG	Date
Microsoft Outlook 2016 Security Technical Implementation Guide	2016-11-02

Details

Check Text ( C-71565r4_chk )
Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Outlook Options -> Mail format -> Internet Formatting "Plain text options" is set to "Enabled" and 'Automatically wrap text at characters' is set to "132" and that a check does not exist in the 'Encode attachments in UUENCODE format' 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\16.0\common\mailsettings\PlainWrapLen is REG_DWORD = 132 (decimal) and the value for HKCU\Software\Policies\Microsoft\Office\16.0\outlook\options\mail\Message Plain Format Mime is REG_DWORD = 1, this is not a finding.

Check Text ( C-71565r4_chk )

Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Outlook Options -> Mail format -> Internet Formatting "Plain text options" is set to "Enabled" and 'Automatically wrap text at characters' is set to "132" and that a check does not exist in the 'Encode attachments in UUENCODE format' 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\16.0\common\mailsettings\PlainWrapLen is REG_DWORD = 132 (decimal) and the value for HKCU\Software\Policies\Microsoft\Office\16.0\outlook\options\mail\Message Plain Format Mime is REG_DWORD = 1, this is not a finding.

Fix Text (F-77469r2_fix)
Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Outlook Options -> Mail format -> Internet Formatting "Plain text options" to "Enabled" and 'Automatically wrap text at characters' to "132" and uncheck the 'Encode attachments in UUENCODE format' check box option.