Comment 193 for bug 52667

Why put the configuration in about:config? Folder-level configuration is not used nearly enough and this screams for folder-level configuration. I filter all my various foo-users mailing lists into separate folders. I often want to reply in those folders to reply-to-list unless otherwise specified. So make the configuration per-folder (with an about:config global, something I wish threading had) along with an option to auto-detect (via scanning list-post, et al) or manually setting. This is how KMail, Claws and mutt all do it. Make the non-default selectable by a dropdown on the button.