private void endMessageHandler() {
        if (this.messageHandler != null) {
            try {
                this.messageHandler.done();
            } catch (final Exception ex) {
                LOGGER.error("done() threw exception", ex);
            }
        }
    }
Safely calls done() on a message hander, if one exists
src/main/java/de/gessnerfl/fakesmtp/smtp/server/Session.java