@Configuration
@PropertySource("classpath:mail.properties")
public class MailingConfig {

    @Value("${mail.protocol}")
    private String mailProtocol;

    @Value("${mail.smtp.host}")
    private String host;

    @Value("${mail.smtp.port}")
    private Integer port;

    @Value("${mail.support.username}")
    private String userName;

    @Value("${mail.support.password}")
    private String password;

    @Bean
    public JavaMailSender javaMailSender() {
        JavaMailSenderImpl javaMailSender = new JavaMailSenderImpl();

        javaMailSender.setProtocol(mailProtocol);
        javaMailSender.setHost(host);
        javaMailSender.setPort(port);
        javaMailSender.setUsername(userName);
        javaMailSender.setPassword(password);

        javaMailSender.setJavaMailProperties(getMailProperties());

        return javaMailSender;
    }

    private Properties getMailProperties() {
        Properties properties = new Properties();
        properties.setProperty("customConfig.smtp.auth", "true");
        properties.setProperty("customConfig.smtp.starttls.enable", "true");
        properties.setProperty("customConfig.debug", "false");
        return properties;
    }
}

mail.protocol=smtp
mail.smtp.host=*****
mail.smtp.port=25
mail.support.username=****
mail.support.password=****

properties.setProperty("customConfig.smtp.auth", "true");
properties.setProperty("customConfig.smtp.starttls.enable", "true");

...

mail.support.username=****
mail.support.password=****

mail.smtp.host="127.0.0.1"