* `mail.close_on_success` configures if page closes on successful send.
* `terminal.font_description` configures font of embedded terminal.
* `terminal.height` configures height of embedded terminal.
* `mail.format_flowed` is off by default.
* Make hooks undoable by providing a field for the inverse command.
* Do not force throw-keyid (follow gpg config).
* Allow GPG to be disabled with configuration option.