Policy
Outlook Rich Text options
This policy setting controls how Outlook sends Rich Text Format (RTF) messages to Internet recipients. If you enable this policy setting, you may choose from the following for handling RTF messages addressed to recipients on the Internet: * Convert to Plain Text format - Outlook converts the message to plain text format in the default character set. Any message formatting will be lost. If you disable or do not configure this policy setting, Outlook automatically converts RTF formatted messages that are sent over the Internet to HTML format, so that the message formatting is maintained and attachments are received.
5f8c61ec17c2 L_OutlookRichTextoptions Registry
Copy registry mappings
HKCU\software\policies\microsoft\office\16.0\outlook\options\mail\message rtf formatPolicy notes
This policy setting controls how Outlook sends Rich Text Format (RTF) messages to Internet recipients. If you enable this policy setting, you may choose from the following for handling RTF messages addressed to recipients on the Internet: * Convert to Plain Text format - Outlook converts the message to plain text format in the default character set. Any message formatting will be lost. If you disable or do not configure this policy setting, Outlook automatically converts RTF formatted messages that are sent over the Internet to HTML format, so that the message formatting is maintained and attachments are received.