* The value is, e.g. root@localhost <br>
     * comment: The common return path of all mail
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getMailReturnPath();

    /**
     * The simple implementation for configuration.
     * @author FreeGen
     */
    public static class SimpleImpl extends ObjectiveConfig implements FessEnv {

        // Test getMailSubjectTestPrefix
        assertEquals("[Test]", fessEnv.getMailSubjectTestPrefix());

        // Test getMailReturnPath
        assertEquals("root@localhost", fessEnv.getMailReturnPath());
    }

    // Test custom properties
    public void xtest_customProperties() {
        // Create custom FessEnv with custom properties

            }

            @Override
            public String getMailFromName() {
                return "Fess Crawler";
            }

            @Override
            public String getMailReturnPath() {
                return "******@****.***";
            }

            @Override
            public Integer getCrawlerSystemMonitorIntervalAsInteger() {
                return 60000;
            }

            return "******@****.***";
        }

        @Override
        public String getMailFromName() {
            return "Fess System";
        }

        @Override
        public String getMailReturnPath() {
            return "******@****.***";
        }
    }

            return "******@****.***";
        }

        @Override
        public String getMailFromName() {
            return "Fess System";
        }

        @Override
        public String getMailReturnPath() {
            return "******@****.***";
        }
    }

                    EsStatusPostcard.droppedInto(postbox, postcard -> {
                        postcard.setFrom(fessConfig.getMailFromAddress(), fessConfig.getMailFromName());
                        postcard.addReplyTo(fessConfig.getMailReturnPath());
                        if (toAddresses.length > 0) {
                            stream(toAddresses).of(stream -> stream.map(String::trim).forEach(address -> {
                                postcard.addTo(address);

        motorbike.registerConnectionInfo(hostPortList.get(0), Integer.parseInt(hostPortList.get(1)));
        motorbike.registerReturnPath(fessConfig.getMailReturnPath());
        parkingLot.registerMotorbikeAsMain(motorbike);
        return parkingLot;
    }

    // -----------------------------------------------------
    //                                      Postal Personnel

                LogNotificationPostcard.droppedInto(postbox, postcard -> {
                    postcard.setFrom(fessConfig.getMailFromAddress(), fessConfig.getMailFromName());
                    postcard.addReplyTo(fessConfig.getMailReturnPath());
                    if (toAddresses.length > 0) {
                        stream(toAddresses).of(stream -> stream.map(String::trim).forEach(address -> {
                            postcard.addTo(address);

        try {
            TestmailPostcard.droppedInto(postbox, postcard -> {
                postcard.setFrom(fessConfig.getMailFromAddress(), fessConfig.getMailFromName());
                postcard.addReplyTo(fessConfig.getMailReturnPath());
                stream(toAddresses).of(stream -> stream.forEach(address -> {
                    postcard.addTo(address);
                }));
                BeanUtil.copyMapToBean(dataMap, postcard);

                CrawlerPostcard.droppedInto(postbox, postcard -> {
                    postcard.setFrom(fessConfig.getMailFromAddress(), fessConfig.getMailFromName());
                    postcard.addReplyTo(fessConfig.getMailReturnPath());
                    if (toAddresses.length > 0) {
                        stream(toAddresses).of(stream -> stream.map(String::trim).forEach(address -> {
                            postcard.addTo(address);