Manage the format of outgoing Outlook messages
Outlook has three message formats to choose from: plain text, HTML, and rich text. You don’t have to specify your preferred format every time you write a message. Instead, make it the default message format in Outlook and automatically apply it to every message.
The instructions in this article apply to Outlook 2019, Outlook 2016, Outlook 2013, Outlook 2010, and Outlook for Office 365.
How to set the default message format in Outlook?
HTML is the default message format in Outlook. Although the plain text format works for all email programs, it does not support text formatting. Rich Text Format (RTF) is only supported by Microsoft Exchange version 4.0 and 5.0 clients and Outlook.
To set the default format for new emails in Outlook:
Go to File † parameters: †
In the dialog box Outlook options select mail †
Click the drop-down arrow Create posts in this format and choose the format you want to use as the default for new emails.
Select Okay †
You can set Outlook to always use plain text or rich text for individual recipients, regardless of the default message format you set.