code: public static Map<Property, Object> loadProperties(final File filename, final boolean addProperties) {
  		try {
  			return loadProperties(new FileInputStream(filename), addProperties);
  		} catch (final FileNotFoundException e) {
  			throw new IllegalStateException("error reading properties file from File", e);
  		}
  	}
docs: Loads properties from property {@link File}, if provided. Calling this method only has effect on new Email and Mailer instances after this.
  
  @param filename      Any file reference that holds a properties list.
  @param addProperties Flag to indicate if the new properties should be added or replacing the old properties.
  @return The updated properties map that is used internally.