/** The key of the configuration. e.g. true */
    String MAIL_SEND_MOCK = "mail.send.mock";

    /** The key of the configuration. e.g. localhost:25 */
    String MAIL_SMTP_SERVER_MAIN_HOST_AND_PORT = "mail.smtp.server.main.host.and.port";

    /** The key of the configuration. e.g. [Test] */
    String MAIL_SUBJECT_TEST_PREFIX = "mail.subject.test.prefix";