Yahoo! two-step authentication with iOS Mail and Apple Mail

I have recently activated two-step authentication for my Yahoo! e-mail account. I am now no longer able to use iOS Mail (on iPhone) or Apple Mail (on macOS) even though I have created third-party app passwords as recommended by Yahoo!. The error messages read "Invalid Password. Please try again." (in Settings | Mail | Accounts | ...@yahoo.com | Re-enter Password) and "Wrong Password. Try again." for iOS Mail and Apple Mail respectively. So how can I successfully configure Yahoo! third-party app passwords into iOS Mail and Apple Mail?