def METHOD_NAME(recipient):
    """ Rewrite the envelope recipient if it is a valid SRS address.
    This is meant for bounces to go back to the original sender.
    """
    srs = srslib.SRS(flask.current_app.srs_key)
    if srslib.SRS.is_srs_address(recipient):
        try:
            return flask.jsonify(srs.reverse(recipient))
        except srslib.Error as error:
            return flask.abort(404)
    return flask.abort(404)