https://secure.phabricator.com/settings/panel/emailpreferences/ yields:
```>>> UNRECOVERABLE FATAL ERROR <<<
Undefined class constant 'MAILTAG_DESCRIPTION'
/core/lib/phabricator/src/applications/countdown/editor/PhabricatorCountdownEditor.php:151
┻━┻ ︵ ¯\_(ツ)_/¯ ︵ ┻━┻```