code: function PostalDataValidator(data) {
    MessagingUserStatus.call(this, 'postal validator');
  
    if (typeof data.to === 'undefined') {
      // No to address given
      this.state.code = this.StatusCodes.MISSING;
      this.state.message = 'No "to" address given';
  
    } else if (typeof data.from === 'undefined') {
      // No from address given
      this.state.code = this.StatusCodes.MISSING;
      this.state.message = 'No "from" address given';
  
    } else if (typeof data.file === 'undefined') {
      // No file given
      this.state.code = this.StatusCodes.MISSING;
      this.state.message = 'No file given';
  
    } else {
      // Input data is valid
      this.state.code = this.StatusCodes.VALID;
      this.state.message = 'Ok';
    }
  }
docs: /*
  Postal validation
  
  @param data         The content of the postal letter