People have become accustomed to sending and receiving rich-text email messages, which feature rich text formatting, inline photos, links, and scenic backgrounds. But plain text still has its uses. Yahoo Mail makes it possible to send both formats.
How to send email as plain text
To compose a text-only message or convert a rich text email to plain text in Yahoo Mail:
Click the Compose button in Yahoo Mail to create a new email message.
Enter the text and other content in the body of the email, then click the three dots icon for more options.