Re: pop-up-frames inconvenience

[Richard Stallman]

    when pop-up-frames is customized to t, the frames proliferate without
    end and have to be explicitly deleted.
    e.g., C-x m (`compose-mail') now creates a new frame that does not go
    away automatically when I hit C-c C-c (`message-send-and-exit').

That is what pop-up-frames does.