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";

    /** The key of the configuration. e.g. root@localhost */
    String MAIL_RETURN_PATH = "mail.return.path";

    /**
     * Get the value of property as {@link String}.

            defaultMap.put(FessConfig.MAIL_SEND_MOCK, "true");
            defaultMap.put(FessConfig.MAIL_SMTP_SERVER_MAIN_HOST_AND_PORT, "localhost:25");
            defaultMap.put(FessConfig.MAIL_SUBJECT_TEST_PREFIX, "[Test]");
            defaultMap.put(FessConfig.MAIL_RETURN_PATH, "root@localhost");
            return defaultMap;
        }
    }

            }

            @Override
            protected OptionalThing<SMailSubjectFilter> createSubjectFilter() {
                return OptionalThing.of((view, subject) -> subject);
            }

            @Override
            protected OptionalThing<SMailAsyncStrategy> createAsyncStrategy() {
                return OptionalThing.of((view, runnable) -> async(asyncManager, runnable));