IMAP mail downloads all folders POP downloads the inbox only.

Thunderbird supports both IMAP and POP, so does Yahoo.

So you need to add your account again as IMAP.

Thanks, Matt! For those looking for the yahoo mail IMAP settings, you can find them here: https://help.yahoo.com/kb/mobile-mail/imap-server-settings-sln4075.html

POP server settings are here: https://sg.help.yahoo.com/kb/mail-for-desktop/pop-server-settings-sln4724.html

I did not list the settings as Thunderbird knows both sets of settings. It is just a matter of selecting the type of service you want, IMAP or POP. Thunderbird can do the rest.

I didn't see that option. I manually reset the email account because it was already set up as POP.