Read signed email as plain text must be enforced.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-251865	DTOO215	SV-251865r811186_rule		Medium

Description
Outlook can display email messages and other items in three formats: plain text, Rich Text Format (RTF), and HTML. By default, Outlook displays digitally signed email messages in the format which they were received.

STIG	Date
Microsoft Outlook 2016 Security Technical Implementation Guide	2022-03-11

Details

Check Text ( C-55325r811184_chk )
Verify the policy value for User Configuration >> Administrative Templates >> Microsoft Outlook 2016 >> Outlook Options >> Preferences >> E-mail Options "Read signed e-mail as plain text" is set to "Enabled". Procedure: Use the Windows Registry Editor to navigate to the following key: HKCU\Software\Policies\Microsoft\Office\16.0\outlook\options\mail Criteria: If the value ReadSignedAsPlain is REG_DWORD = 1, this is not a finding.

Check Text ( C-55325r811184_chk )

Verify the policy value for User Configuration >> Administrative Templates >> Microsoft Outlook 2016 >> Outlook Options >> Preferences >> E-mail Options "Read signed e-mail as plain text" is set to "Enabled".

Procedure: Use the Windows Registry Editor to navigate to the following key:

HKCU\Software\Policies\Microsoft\Office\16.0\outlook\options\mail

Criteria: If the value ReadSignedAsPlain is REG_DWORD = 1, this is not a finding.

Fix Text (F-55279r811185_fix)
Set the policy value for User Configuration >> Administrative Templates >> Microsoft Outlook 2016 >> Outlook Options >> Preferences >> E-mail Options "Read signed e-mail as plain text" to "Enabled".