https://support.microsoft.com/en-us/office/change-the-default-font-or-text-color-for-email-messages-in-outlook-1aabb236-01d4-4faf-b998-a4087da3ceab
You can change the default font and its color, size, and style — such as bold or italic. Outlook allows you to change the font, color, size, and style for new messages and replie