Saving Yahoo Mail messages to a .txt file now requires a workaround
Yahoo Mail Classic includes a feature that allows you to save the contents of an email as a text file on your computer. While current versions of Yahoo Mail no longer support text export, you can use a workaround to save messages offline.
The instructions in this article apply to using Yahoo Mail on the web on a Windows or Mac computer.
Save Yahoo Mail Text to File
While you can safely store and organize emails using your custom Yahoo Mail folders, you may prefer that messages are stored on your computer so that you can access them offline. Since you can no longer load a text copy into a .txt file, you have to resort to copying and pasting:
Open the message in Yahoo Mail.
Highlight the body of the email with the cursor, then use ctrl + C (PC) or order + C Strong > (Mac) keyboard shortcut for copying text.
Open a word processing program on your computer such as Notepad on Windows or TextEdit on macOS and create a new file.
Click in the text file and click ctrl + V (PC) or order + V (Mac) to paste. copied text.
Save the file with a name that matches its contents.