When you create new e-mail messages, you can specify the format in which the message should be created. The format you choose must be supported by the recipient of the message. Outlook also allows you to set up your environment so that all your messages use the same format. You can choose from Plain Text, Rich Text, or HTML as the default.
Create a new message.
Click the Options tab on the ribbon.
Choose a format from the Format group:
Choose Plain Text to create a message without formatting. ...