A lot of boilerplate is needed to load a configuration file with Joran. I suggest improving doConfigure to support scanning inputs on the classpath. Sample code of 7 lines could be condensed to two.

LoggerContext context = (LoggerContext) LoggerFactory.getILoggerFactory();

JoranConfigurator configurator = new JoranConfigurator();
configurator.setContext(context);
context.reset();

InputStream inputStream = SmtpTest.class.getClassLoader().getResourceAsStream(INPUT_FILE);
if(inputStream == null) throw new IllegalStateException("File not found: " + INPUT_FILE);
configurator.doConfigure(inputStream);

VS

JoranConfigurator configurator = new JoranConfigurator();
configurator.doConfigure(INPUT_FILE);